Change MCexeccontexts to MCExecContext[] (from MCExecPoint[])

The debugging code was also reworked to take ctxt parameters instead of EP parameters.
Server debugging EP->ctxt replacements
Replace MCEPptr with MCECptr

The pointers are equivalent only the new global is an MCExecContext instead of an MCExecPoint
Fix a couple of oversights preventing mobile platforms from building
Merge branch 'refactor-syntax_unicode' into refactor-syntax_unicode_execcontexts
Merge branch 'refactor-syntax_unicode' into refactor-syntax_unicode_execcontexts

Conflicts:
	engine/src/debug.cpp
	engine/src/mode_development.cpp
Merge branch 'refactor-syntax_unicode' into refactor-syntax_unicode_execcontexts

Conflicts:
	engine/src/debug.cpp
Implement MCVariable::copyasvalueref
Change MCU_{encode,decode}base64 to no longer use an EP
Merge remote-tracking branch 'upstream/refactor-syntax_unicode' into refactor-syntax_unicode_execcontexts

Conflicts:
	engine/src/debug.cpp
	engine/src/debug.h
	engine/src/statemnt.cpp
	engine/src/variable.cpp
Merge remote-tracking branch 'upstream/refactor-syntax_unicode' into refactor-syntax_unicode_execcontexts

Conflicts:
	engine/src/util.h
Merge remote-tracking branch 'upstream/refactor-syntax_unicode' into refactor-syntax_unicode_execcontexts