Log Message:
libass: update to 0.17.2.

libass (0.17.2)
 * Fix rendering of \h in certain cases
 * Fix a minor memory leak in the CoreText and DirectWrite font provider
 * Fix wrong ASS_Image dimensions for huge BorderStyle=4 backgrounds
   potentially leading to out of bound reads by API users

 * Improve quality of animated rectangular clips
 * Improve accuracy of cache limits
 * Full-Unicode cmaps are now always preferred
 * Improve font selection compatibility in the DirectWrite font provider
 * Improved documentation
   * Color mangling notes in ass_types.h were updated for tone mapping and HDR video
   * Guidelines for producing portable ASS files can now be found in our wiki

 * Updating selective overrides now forces a cache clear to avoid issues with \ 
outdated caches
 * Frame and storage resolutions are now limited to what a single ASS_Image can \ 
represent
 * make check now runs checkasm if assembly is enabled
 * CoreText can now be used on Mac OS X 10.5
 * Meson/muon is now offered as a secondary build system bringing back \ 
first-party MSVC support
   Note however it is not at feature parity with autotools in all cases

 * aarch64: add optimized assembly routines covering the same set as on x86;
   they work on both little and big endian systems
 * x86: add SSSE3 versions of some assembly routines to help CPUs without AVX2
 * x86: it is now possible to build binaries with optimized assembly and SHSTK \ 
support

 * Improve VSFilter compatibility:
   * Trailing spaces are no longer trimmed from style and
     event string fields (this does not affect Text)
   * All BiDi paragraph separators now delimit BiDi runs
   * Fix treatment of font weights < 10
   * Match GDI's faux italic slant
   * Employ faux italics and faux bolding in the same cases as GDI
   * Better match font selection with regard to italic and weight
   * Treat empty Style name as "Default"
   * Various drawing fixes
     * Reject drawings not starting with a valid m command or invalid m followed \ 
by valid n
     * Drop coordinates following invalid commands rather than appending them to \ 
the prior command
     * Ignore p commands without enough preceding nodes
     * Partially fix s and p commands used outside of a properly closed b-spline \ 
sequence