keysym: use a perfect hash function for case sensitive xkb_keysym_from_name

keysym: use a perfect hash function for case sensitive xkb_keysym_from_name

In 7d84809fdccbb5898d0838849ec7c321410182d5 I added a fast path for the
case-sensitive case, but it is still slowing down Compose parsing.

Instead of the binary search, use a perfect hash function, computed with
a simple python module I found (vendored).

It is faster -- perf diff is:

   Baseline  Delta Abs  Shared Object      Symbol
   ........  .........  .................  ...................................

     22.35%    -14.04%  libc-2.33.so       [.] __strcmp_avx2
     16.75%    +10.28%  bench-compose      [.] xkb_keysym_from_name
     20.72%     +2.40%  bench-compose      [.] parse.constprop.0
      2.29%     -1.97%  bench-compose      [.] strcmp@plt
      2.56%     +1.81%  bench-compose      [.] resolve_name
      2.37%     +0.92%  libc-2.33.so       [.] __GI_____strtoull_l_internal
     26.19%     -0.63%  bench-compose      [.] lex
      1.45%     +0.56%  libc-2.33.so       [.] __memchr_avx2
      1.13%     -0.31%  libc-2.33.so       [.] __strcpy_avx2

Also reduces the binary size:

Before:

      text    data     bss     dec     hex filename
    341111    5064       8  346183   54847 build/libxkbcommon.so.0.0.0

After:

      text    data     bss     dec     hex filename
    330215    5064       8  335287   51db7 build/libxkbcommon.so.0.0.0

Note however that it's still larger than before 7d84809fdccbb5898d08388:

      text    data     bss     dec     hex filename
    320617    5168       8  325793   4f8a1 build/libxkbcommon.so.0.0.0

Signed-off-by: Ran Benita <ran@unusedvar.com>