[sfnt] Implement support for `OS/2' table version 5.

See

  http://typedrawers.com/discussion/470/new-microsoft-size-specific-design-selection-mechanism

for the announcement.

* include/freetype/tttables.h (TT_OS2): Add fields
`usLowerPointSize' and `usUpperPointSize'.  Since FreeType returns
this structure only as a pointer through `FT_Get_Sfnt_Table', there
shouldn't be any ABI problems.

* src/sfnt/ttload.c (tt_face_load_os2): Implement it.

* docs/CHANGES: Updated.
Comment fixes.
Comment fix.
[truetype] Minor code refactoring.

Two benefits: The allocated FDEF (and IDEF) array gets slightly
smaller, and the `ttdebug' demo program has access to function
numbers without additional costs.

Fortunately, no changes to FontForge are necessary – this is the
only external TrueType debugger I know of, but others may exist and
should check the code accordingly.

* src/truetype/ttinterp.h (TT_CallRec): Replace `Cur_Restart' and
`Cur_End' with a pointer to the corresponding `TT_DefRecord'
structure.

* src/truetype/ttinterp.c (DO_JROT, DO_JMPR, DO_JROF, Ins_ENDF,
Ins_CALL, Ins_LOOPCALL, Ins_UNKNOWN, TT_RunIns <Invalid_Opcode>):
Updated.
* docs/CHANGES: Updated.
Fix Savannah bug #40451.

Simply apply the patch from the bug report.

* builds/unix/ftconfig.in, builds/vms/ftconfig.h,
include/freetype/config/ftconfig.h: The used #pragma directives only
work with gcc versions 4.6 and higher.
[truetype] Fix GETINFO opcode handling of subpixel hinting bits.

* src/truetype/ttinterp.c (Ins_GETINFO): Don't request bit 6 set to
get info on subpixel hinting.

* docs/CHANGES: Updated.
Typos.