Update libsass to 3.6.5
Changes:
- Fix extend edge case going endlessly
- Fix source-maps and how we count unicode characters
- Fix seed generator if std::random_device fails
- Fix url() containing exclamation mark causing an error
- Fix Offset initialization when end was not given
- Fix obvious backporting error in pseudo extend
- Fix obvious identical subexpressions in op_color_number
- Fix edge case regarding unit-less number equality as object keys
- Prevent compiler warning about unnecessary copy
- Fix parenthesization for selector schema and real parents
- Add deprecation warning for global variable creation
- Handle loaded source code as shared objects
- Add back C-API getters for plugin paths
- Fix compound extend warning
- Extend error_src lifetime on C-API context
- Preserve indentation in nested mode
- Improve pseudo selector handling
- Fix "call" for $function
- Fix various functions arguments
- Check weight argument on invert call
- Fix bug in scale-color with positive saturation
- Fix selector isInvisible logic
- Fix evaluation of unary expressions in loops
- Fix attribute selector equality with modifiers
- Fix memory leaks, crashes, segfaults