granular verbose message suppression mechanics

Switch to using a macro invocation Verbos(n, s) in place of the
flags.verbose checks.

Provide the mechanics for individual suppression of any of the
existing messages that were considered verbose.

Mechanics only - this code update does not provide any means of
setting the suppression bits.

iflags.verbose = 0
is still a master suppression of all the verbose messages.

iflags.verbose = 1
turns on the verbose messages only for those whose suppression
bit is 0 (not set).

src/polyself.c

@@ -844,7 +844,7 @@ polymon(int mntmp)
             dismount_steed(DISMOUNT_POLY);
     }
 
-    if (flags.verbose) {
+    if (Verbose(2, polymon)) {
         static const char use_thec[] = "Use the command #%s to %s.";
         static const char monsterc[] = "monster";
         struct permonst *uptr = g.youmonst.data;