Merge branch 'master' into gonesolong

Conflicts:
	src/CMakeLists.txt
	src/b_think.cpp
	src/g_doom/a_doomweaps.cpp
	src/g_hexen/a_clericstaff.cpp
	src/g_hexen/a_fighterplayer.cpp
	src/namedef.h
	src/p_enemy.cpp
	src/p_local.h
	src/p_mobj.cpp
	src/p_teleport.cpp
	src/sc_man_tokens.h
	src/thingdef/thingdef_codeptr.cpp
	src/thingdef/thingdef_function.cpp
	src/thingdef/thingdef_parse.cpp
	wadsrc/static/actors/actor.txt
	wadsrc/static/actors/constants.txt
	wadsrc/static/actors/shared/inventory.txt

- Added register reuse to VMFunctionBuilder for FxPick's code emitter.
- Note to self: Need to reimplement IsPointerEqual and CheckClass, which
  were added to thingdef_function.cpp over the past year, as this file no
  longer exists in this branch.

src/zscript/vmbuilder.cpp

@@ -279,7 +279,7 @@ VMFunctionBuilder::RegAvailability::RegAvailability()
 
 //==========================================================================
 //
-// VMFunctionBuilder :: RegAvailibity :: Get
+// VMFunctionBuilder :: RegAvailability :: Get
 //
 // Gets one or more unused registers. If getting multiple registers, they
 // will all be consecutive. Returns -1 if there were not enough consecutive
@@ -411,6 +411,30 @@ void VMFunctionBuilder::RegAvailability::Return(int reg, int count)
 	}
 }
 
+//==========================================================================
+//
+// VMFunctionBuilder :: RegAvailability :: Reuse
+//
+// Marks an unused register as in-use. Returns false if the register is
+// already in use or true if it was successfully reused.
+//
+//==========================================================================
+
+bool VMFunctionBuilder::RegAvailability::Reuse(int reg)
+{
+	assert(reg >= 0 && reg <= 255);
+
+	VM_UWORD mask = reg & 31;
+	int word = reg / 32;
+
+	if (Used[word] & mask)
+	{ // It's already in use!
+		return false;
+	}
+	Used[word] |= mask;
+	return true;
+}
+
 //==========================================================================
 //
 // VMFunctionBuilder :: Emit