Updates on MCScreenDC and MCUIDC methods
Merge branch 'refactor-syntax_unicode_MCScreenDC' of https://github.com/runrevpanos/livecode into refactor-syntax_unicode_MCScreenDC
Did some modifications and now it compiles and runs ok on Mac Desktop
Add basic implementation of MCStringGetCodepointAtIndex

Does not yet support UTF-16 with surrogate pairs!
Convert most users of MCFontMeasureText to use StringRefs

A number of CString users remain in block.cpp.
Add utility function MCU_r8tos

Required by the scrollbar drawing code.
Updates on MCObject and MCStack methods. On Mac Desktop, it compiles and runs, but when the first window pops up, there is no close (X) button
Simplify MCControl::setsbprop function and remove MCU_matchflags

Only two callers of setsbprop exist in (non-LEGACY_EXEC) code and they only use two properties rather than the myriad supported in the code.
Add copyasstring method to MCError

Copies the contents of the error as a StringRef.
Method MCUIDC::delaymessage now takes StringRef arguments

Arguments converted from const char* to StringRef.
Update opensslsocket.cpp to remove calls to MCParameter::setbuffer
Replace calls to MCParameter::setbuffer in player.cpp
[[ UnicodifyScript ]] Updated object 'script' instance variable to MCStringRef.
[[ UnicodifyScript ]] Updated MCScriptPoint to tokenize UTF-8 and convert as appropriate.
Merge branch 'refactor-syntax_unicode_fontdraw' of https://github.com/runrevfraser/livecode into refactor-syntax_unicode_fontdraw
[[ UnicodifyGroup ]] Moved flag updating from MCGroup::load to MCGroup::save.
Merge branch 'refactor-syntax_unicode_setbuffer' of https://github.com/runrevfraser/livecode into refactor-syntax_unicode_setbuffer
[[ UnicodifyError ]] Changed copyasstring to copyasstringref for consistency with elsewhere.
Merge branch 'refactor-syntax_unicode_setsbprop' of https://github.com/runrevfraser/livecode into refactor-syntax_unicode_setsbprop
Merge branch 'refactor-syntax_unicode_MCScreenDC' of https://github.com/runrevpanos/livecode into refactor-syntax_unicode_screendc
[[ UnicodifyScreenDC ]] Reverted textwidth() signature changes.