[[ stonCache ]] Implements storing/fetching the number value from a stringRef during string_to_num conversions
[[ stonCache ]] Remove caching for octals conversion
[[ stonCache ]] STON cache now located after the last char
[[ stonCache ]] Ensure the numeric value is stored o at an 8-byte aligned position
Ensure native char is mapped to unicode codepoint in MCStringGetCodepointAtIndex
Fix filter command false negatives
Fix split command
Fix unicode last index of char
Merge branch 'refactor-syntax_unicode' of https://github.com/runrev/livecode into feature-tab_alignments
Fix findwordbreakbefore when given index is 0
Merge pull request #699 from runrevsebastien/refactor-syntax_unicode_ston

Refactor syntax unicode ston
Ensure strings never 'contain' empty
Merge branch 'refactor-syntax_unicode' into feature-tab_alignments
Rename existing MCSegment to MCLineSegment
Disable existing tab-handling code

Because it hasn't been replaced, tabs do not work at all, currently...
Initial support for the segment-based tab system

Still buggy but I'd better commit before I break something...

Outstanding issues:

1. Padding problem with right-aligned text (see script line count in project browser)
2. Crash when opening application browser (related to the grid layout it uses)
3. Not at all tested with RTL text
4. Only slightly tested with LTR text
Fix segments having their horizontal alignment unset
Fix a leak of segment objects
Update the parent pointer of segments when assigned to a different line
Fix segment splitting when doing wrapping