Build rules changes to allow building on XCode 3 and 4
Merge remote-tracking branch 'upstream/refactor-syntax_unicode' into refactor-syntax_unicode
Fix a crash bug due to a nullptr dereference

Caused crashes when setting the contents of a field.
Fix to MCStringConvertToCFStringRef

Wrong character encoding was being used.
Merge branch 'refactor-syntax_unicode_squash0' of https://github.com/runrevfraser/livecode into refactor-syntax_unicode
Tweaked Mac desktop project and global xcconfig to use system default compiler.
Fixed compilation of installer related files.