Re-fix altar compiler warning

Implement a better fix for commit 2f4f7d22d ("Fix align type
mixup wth align mask") which was reverted in commit 4e35e8b5a
("Revert "Fix align type mixup wth align mask"").

In the present code, the field align in both struct altar and
struct monster is not an aligntyp, but an align mask with extra flags.
Change the type to match its actual use and improve the naming.

Consolidate duplicated code into a single routine.

Change the return type of induced_align() to be unsigned to match
amask usage.

Change the special level align mask values to be separate from
the normal align mask values.

src/dungeon.c

@@ -1869,7 +1869,8 @@ assign_rnd_level(d_level *dest, d_level *src, int range)
         dest->dlevel = 1;
 }
 
-int
+/* return an alignment mask */
+unsigned int
 induced_align(int pct)
 {
     s_level *lev = Is_special(&u.uz);

src/sp_lev.c

@@ -49,6 +49,7 @@ static void create_trap(spltrap *, struct mkroom *);
 static int noncoalignment(aligntyp);
 static boolean m_bad_boulder_spot(int, int);
 static int pm_to_humidity(struct permonst *);
+static unsigned int sp_amask_to_amask(unsigned int sp_amask);
 static void create_monster(monster *, struct mkroom *);
 static void create_object(object *, struct mkroom *);
 static void create_altar(altar *, struct mkroom *);
@@ -1758,13 +1759,36 @@ pm_to_humidity(struct permonst* pm)
     return loc;
 }
 
+/*
+ * Convert a special level alignment mask (an alignment mask with possible
+ * extra values/flags) to a "normal" alignment mask (no extra flags).
+ *
+ * When random: there is an 80% chance that the altar will be co-aligned.
+ */
+static unsigned int
+sp_amask_to_amask(unsigned int sp_amask)
+{
+    unsigned int amask;
+
+    if (sp_amask == AM_SPLEV_CO)
+        amask = Align2amask(u.ualignbase[A_ORIGINAL]);
+    else if (sp_amask == AM_SPLEV_NONCO)
+        amask = Align2amask(noncoalignment(u.ualignbase[A_ORIGINAL]));
+    else if (sp_amask == AM_SPLEV_RANDOM)
+        amask = induced_align(80);
+    else
+        amask = sp_amask & AM_MASK;
+
+    return amask;
+}
+
 static void
 create_monster(monster* m, struct mkroom* croom)
 {
     struct monst *mtmp;
     xchar x, y;
     char class;
-    aligntyp amask;
+    unsigned int amask;
     coord cc;
     struct permonst *pm;
     unsigned g_mvflags;
@@ -1777,13 +1801,7 @@ create_monster(monster* m, struct mkroom* croom)
     if (class == MAXMCLASSES)
         panic("create_monster: unknown monster class '%c'", m->class);
 
-    amask = (m->align == AM_SPLEV_CO)
-               ? Align2amask(u.ualignbase[A_ORIGINAL])
-               : (m->align == AM_SPLEV_NONCO)
-                  ? Align2amask(noncoalignment(u.ualignbase[A_ORIGINAL]))
-                  : (m->align == AM_SPLEV_RANDOM)
-                     ? induced_align(80)
-                     : m->align;
+    amask = sp_amask_to_amask(m->sp_amask);
 
     if (!class)
         pm = (struct permonst *) 0;
@@ -1823,7 +1841,7 @@ create_monster(monster* m, struct mkroom* croom)
     if (croom && !inside_room(croom, x, y))
         return;
 
-    if (m->align != AM_SPLEV_RANDOM)
+    if (m->sp_amask != AM_SPLEV_RANDOM)
         mtmp = mk_roamer(pm, Amask2align(amask), x, y, m->peaceful);
     else if (PM_ARCHEOLOGIST <= m->id && m->id <= PM_WIZARD)
         mtmp = mk_mplayer(pm, x, y, FALSE);
@@ -2261,7 +2279,7 @@ create_altar(altar* a, struct mkroom* croom)
 {
     schar sproom;
     xchar x = -1, y = -1;
-    aligntyp amask;
+    unsigned int amask;
     boolean croom_is_temple = TRUE;
     int oldtyp;
 
@@ -2282,20 +2300,7 @@ create_altar(altar* a, struct mkroom* croom)
     if (oldtyp == STAIRS || oldtyp == LADDER)
         return;
 
-    /* Is the alignment random ?
-     * If so, it's an 80% chance that the altar will be co-aligned.
-     *
-     * The alignment is encoded as amask values instead of alignment
-     * values to avoid conflicting with the rest of the encoding,
-     * shared by many other parts of the special level code.
-     */
-    amask = (a->align == AM_SPLEV_CO)
-               ? Align2amask(u.ualignbase[A_ORIGINAL])
-               : (a->align == AM_SPLEV_NONCO)
-                  ? Align2amask(noncoalignment(u.ualignbase[A_ORIGINAL]))
-                  : (a->align == AM_SPLEV_RANDOM)
-                     ? induced_align(80)
-                     : a->align;
+    amask = sp_amask_to_amask(a->sp_amask);
 
     levl[x][y].typ = ALTAR;
     levl[x][y].altarmask = amask;
@@ -3008,7 +3013,7 @@ lspo_monster(lua_State* L)
     tmpmons.name.str = NULL;
     tmpmons.appear = 0;
     tmpmons.appear_as.str = (char *) 0;
-    tmpmons.align = AM_SPLEV_RANDOM;
+    tmpmons.sp_amask = AM_SPLEV_RANDOM;
     tmpmons.female = 0;
     tmpmons.invis = 0;
     tmpmons.cancelled = 0;
@@ -3073,7 +3078,7 @@ lspo_monster(lua_State* L)
         tmpmons.name.str = get_table_str_opt(L, "name", NULL);
         tmpmons.appear = 0;
         tmpmons.appear_as.str = (char *) 0;
-        tmpmons.align = get_table_align(L);
+        tmpmons.sp_amask = get_table_align(L);
         tmpmons.female = get_table_int_opt(L, "female", 0);
         tmpmons.invis = get_table_int_opt(L, "invisible", 0);
         tmpmons.cancelled = get_table_int_opt(L, "cancelled", 0);
@@ -3907,7 +3912,7 @@ lspo_altar(lua_State* L)
         acoord = SP_COORD_PACK(x, y);
 
     tmpaltar.coord = acoord;
-    tmpaltar.align = al;
+    tmpaltar.sp_amask = al;
     tmpaltar.shrine = shrine;
 
     create_altar(&tmpaltar, g.coder->croom);