distinguish global variables that get written to savefile

The g? structs had a mix of variables that were written to
the savefile, and those that were not.

For better clarity and to distinguish those that end up in
the savefile, relocate some g? variables that get written
directly to the savefile into different structs.

This updates EDITLEVEL, although technically it probably
didn't need to, since savefile contents are not changing.

Details:

    gb.bases            -> svb.bases
    gb.bbubbles         -> svb.bbubbles
    gb.branches         -> svb.branches
    gc.context          -> svc.context
    gd.disco            -> svd.disco
    gd.dndest           -> svd.dndest
    gd.doors            -> svd.doors
    gd.doors_alloc      -> svd.doors_alloc
    gd.dungeon_topology -> svd.dungeon_topology
    gd.dungeons         -> svd.dungeons
    ge.exclusion_zones  -> sve.exclusion_zones
    gh.hackpid          -> svh.hackpid
    gi.inv_pos          -> svi.inv_pos
    gk.killer           -> svk.killer
    gl.lastseentyp      -> svl.lastseentyp
    gl.level            -> svl.level
    gl.level_info       -> svl.level_info
    gm.mapseenchn       -> svm.mapseenchn
    gm.moves            -> svm.moves
    gm.mvitals          -> svm.mvitals
    gn.n_dgns           -> svn.n_dgns
    gn.n_regions        -> svn.n_regions
    gn.nroom            -> svn.nroom
    go.oracle_cnt       -> svo.oracle_cnt
    gp.pl_character     -> svp.pl_character
    gp.pl_fruit         -> svp.pl_fruit
    gp.plname           -> svp.plname
    gp.program_state    -> svp.program_state
    gq.quest_status     -> svq.quest_status
    gr.rooms            -> svr.rooms
    gs.sp_levchn        -> svs.sp_levchn
    gs.spl_book         -> svs.spl_book
    gt.timer_id         -> svt.timer_id
    gt.tune             -> svt.tune
    gu.updest           -> svu.updest
    gx.xmax             -> svx.xmax
    gx.xmin             -> svx.xmin
    gy.ymax             -> svy.ymax
    gy.ymin             -> svy.ymin

Related note:
There are some pointer variables that are heads of chains that were not
moved from 'g?' to 'sv?', because they are not actually written to the
savefile directly, but the objects/monst/trap/lightsource/timer in the
chains they point to are. That can be changed, if desired.
Examples: gi.invent, gm.migrating_objs, gb.billobjs, gm.migrating_mons,
          gf.ftrap, gl.light_base, gt.timer_base

sys/windows/windmain.c

@@ -704,17 +704,17 @@ _CrtSetReportFile(_CRT_ASSERT, _CRTDBG_FILE_STDERR);*/
         (*utf8graphics_mode_callback)();
 #endif
 
-    /* strip role,race,&c suffix; calls askname() if gp.plname[] is empty
+    /* strip role,race,&c suffix; calls askname() if svp.plname[] is empty
        or holds a generic user name like "player" or "games" */
     plnamesuffix();
-    set_playmode(); /* sets gp.plname to "wizard" for wizard mode */
+    set_playmode(); /* sets svp.plname to "wizard" for wizard mode */
     /* until the getlock code is resolved, override askname()'s
        setting of renameallowed; when False, player_selection()
        won't resent renaming as an option */
     iflags.renameallowed = FALSE;
     /* Obtain the name of the logged on user and incorporate
      * it into the name. */
-    Sprintf(fnamebuf, "%s", gp.plname);
+    Sprintf(fnamebuf, "%s", svp.plname);
     (void) fname_encode(
         "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz_-.", '%',
         fnamebuf, encodedfnamebuf, BUFSZ);
@@ -732,8 +732,8 @@ _CrtSetReportFile(_CRT_ASSERT, _CRTDBG_FILE_STDERR);*/
     if (!nhfp) {
         raw_print("Cannot create lock file");
     } else {
-        gh.hackpid = GetCurrentProcessId();
-        (void) write(nhfp->fd, (genericptr_t) &gh.hackpid, sizeof(gh.hackpid));
+        svh.hackpid = GetCurrentProcessId();
+        (void) write(nhfp->fd, (genericptr_t) &svh.hackpid, sizeof(svh.hackpid));
         close_nhfile(nhfp);
     }
     /*
@@ -771,8 +771,8 @@ attempt_restore:
                 }
             }
         }
-        if (gp.program_state.in_self_recover) {
-            gp.program_state.in_self_recover = FALSE;
+        if (svp.program_state.in_self_recover) {
+            svp.program_state.in_self_recover = FALSE;
             set_savefile_name(TRUE);
         }
     }
@@ -923,11 +923,11 @@ process_options(int argc, char * argv[])
 #endif
         case 'u':
             if (argv[0][2])
-                (void) strncpy(gp.plname, argv[0] + 2, sizeof(gp.plname) - 1);
+                (void) strncpy(svp.plname, argv[0] + 2, sizeof(svp.plname) - 1);
             else if (argc > 1) {
                 argc--;
                 argv++;
-                (void) strncpy(gp.plname, argv[0], sizeof(gp.plname) - 1);
+                (void) strncpy(svp.plname, argv[0], sizeof(svp.plname) - 1);
             } else
                 raw_print("Player name expected after -u");
             break;
@@ -1052,7 +1052,7 @@ port_help(void)
 boolean
 authorize_wizard_mode(void)
 {
-    if (!strcmp(gp.plname, WIZARD_NAME))
+    if (!strcmp(svp.plname, WIZARD_NAME))
         return TRUE;
     return FALSE;
 }
@@ -1417,8 +1417,8 @@ gotlock:
               gf.fqn_prefix[LEVELPREFIX]);
         raw_print(oops);
     } else {
-        if (write(fd, (char *) &gh.hackpid, sizeof(gh.hackpid))
-            != sizeof(gh.hackpid)) {
+        if (write(fd, (char *) &svh.hackpid, sizeof(svh.hackpid))
+            != sizeof(svh.hackpid)) {
 #if defined(CHDIR) && !defined(NOCWD_ASSUMPTIONS)
             chdirx(orgdir, 0);
 #endif