[gdb/build] Fix YYSTYPE and yyalloc odr violation

[gdb/build] Fix YYSTYPE and yyalloc odr violation

When building gdb with -O2 -flto I run into:
...
ada-exp.c.tmp:576:7: error: type ‘union YYSTYPE’ violates the C++ One \
  Definition Rule [-Werror=odr]
...

Fix this by renaming to ada_exp_YYSTYPE and likewise for other .y files.

Likewise for yyalloc.

Tested on x86_64-linux.  Also tested with byacc rather than bison on
suggestion of Tom Tromey.

Approved-By: Tom Tromey <tom@tromey.com>
PR build/22395
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=22395