[[ Clean up ]] Factor out common code in MCExecContext
[[ Clean up ]] Factor out common EnsureISAllowed code.
Merge remote-tracking branch 'stephen/refactor-syntax_unicode_ec_tidy' into refactor-syntax_unicode

Conflicts:
	engine/src/exec.cpp
Fixes Android target selection broken on Linux
Bump the version number for 7.0.0-dp-4
Fix erroneous shortcut in MCStringIsEqualTo
Merge branch 'refactor-syntax_unicode' of https://github.com/runrev/livecode into refactor-syntax_unicode
Add nil pointer check to MCGo shim
Merge branch 'refactor-syntax_unicode' of https://github.com/runrev/livecode into refactor-syntax_unicode