- Changed compilation for g_doom, g_heretic, g_hexen and g_strife folders

so that all files are included by a central one instead of compiling 
  each one separately. This speeds up the compilation process by 25%
  when doing a complete rebuild in Visual C.
- Cleaned up more header dependencies.

SVN r1226 (trunk)

src/g_doom/a_doommisc.cpp

@@ -1,6 +1,5 @@
 #include "actor.h"
 #include "info.h"
-#include "p_enemy.h"
 #include "p_local.h"
 #include "a_sharedglobal.h"
 #include "m_random.h"
@@ -8,6 +7,31 @@
 #include "doomstat.h"
 #include "gstrings.h"
 #include "thingdef/thingdef.h"
+#include "g_level.h"
+#include "p_enemy.h"
+#include "a_doomglobal.h"
+#include "a_specialspot.h"
+#include "templates.h"
+#include "m_bbox.h"
+
+// Include all the other Doom stuff here to reduce compile time
+#include "a_arachnotron.cpp"
+#include "a_archvile.cpp"
+#include "a_bossbrain.cpp"
+#include "a_bruiser.cpp"
+#include "a_cacodemon.cpp"
+#include "a_cyberdemon.cpp"
+#include "a_demon.cpp"
+#include "a_doomimp.cpp"
+#include "a_doomweaps.cpp"
+#include "a_fatso.cpp"
+#include "a_keen.cpp"
+#include "a_lostsoul.cpp"
+#include "a_painelemental.cpp"
+#include "a_possessed.cpp"
+#include "a_revenant.cpp"
+#include "a_spidermaster.cpp"
+#include "a_scriptedmarine.cpp"
 
 // The barrel of green goop ------------------------------------------------