HyperRogue 13.1o: fixes for the web build (mymake -web), which no longer compiled.

- basegraph.cpp: debug_init_font was defined only with SDL_ttf, but init_glfont uses it with the
  built-in font too (CAP_TABFONT, the web build); the TTF_GlyphIsProvided check needs SDL_ttf and
  now stays inside the #if that already excluded the rest of the TTF code;
- legacy.cpp: the music debug flags only exist with audio (CAP_SDLAUDIO), which the web build has not;
- geom-exp.cpp: showQuotientConfig3 only exists with CAP_THREAD && MAXMDIM >= 4 (not on the web);
  "-d:quotient" falls back to the 2D dialog there.

Part of the source of the build served at fredygames.com (GPL-2.0-or-later, like HyperRogue).

--- a/basegraph.cpp
+++ b/basegraph.cpp
@@ -218,6 +218,8 @@
 
 #endif
 
+EX debugflag debug_init_font = {"init_font", true};
+
 #if CAP_SDLTTF
 
 EX vector<string> font_filenames = {
@@ -243,8 +245,6 @@
 EX int last_font_id = 0;
 EX int font_id = 0;
 
-EX debugflag debug_init_font = {"init_font", true};
-
 #ifdef FONTCONFIG
 TTF_Font* findfont(int siz) {
 
@@ -623,7 +623,6 @@
 #endif
     sdltogl(txt, f, ch);
     SDL_DestroySurface(txt);
-#endif
 
     if(ch >= 128 && !TTF_GlyphIsProvided(cfont->font[siz], unicode_value(natchars[ch-128], 0).first)) {
       string s = natchars[ch - 128];
@@ -639,6 +638,7 @@
         if(s[0] == dialog::foreign_letters[2*j] && s[1] == dialog::foreign_letters[2*j+1])
           f.reps[ch] = strdup((string("") + char(dialog::latin_letters[j])).c_str());
       }
+#endif
 
     }
 
--- a/legacy.cpp
+++ b/legacy.cpp
@@ -438,7 +438,9 @@
 vector<legacy_flag> legacy_flags = {
   // INIT
   legacy_flag{'i', 1, &debug_init},
+#if CAP_SDLAUDIO
   legacy_flag{'i', 1, &debug_init_music},
+#endif
   legacy_flag{'i', 1, &debug_init_graph},
   legacy_flag{'i', 1, &debug_init_joy},
   legacy_flag{'i', 1, &debug_init_cells},
@@ -451,7 +453,9 @@
   legacy_flag{'w', 1, &debug_map_warnings},
   // ERROR
   legacy_flag{'e', 1, &debug_errors},
+#if CAP_SDLAUDIO
   legacy_flag{'e', 1, &debug_music_error},
+#endif
   legacy_flag{'e', 1, &debug_joy_error},
   // STEAM
   legacy_flag{'s', 3, &debug_achievements},
--- a/geom-exp.cpp
+++ b/geom-exp.cpp
@@ -1435,8 +1435,13 @@
     shift(); reg3::ultra_mirror_on = argi();
     }
   #endif
+  #if CAP_THREAD && MAXMDIM >= 4
   else if(argis("-d:quotient")) 
     launch_dialog(WDIM == 2 ? showQuotientConfig : showQuotientConfig3);
+  #else
+  else if(argis("-d:quotient")) 
+    launch_dialog(showQuotientConfig);
+  #endif
   else if(argis("-uqf")) 
     fieldpattern::use_quotient_fp = true;
   #endif