* Makefile.in: Sort header definitions.

* Makefile.in: Sort header definitions.
(parser_defs_h, dis_asm_h, annotate_h, gdbthread_h): Define.
Replace parser-defs.h with $(parser_defs_h).  Replace $(dis-asm_h)
and $(dis-asm.h) with $(dis_asm_h).  Replace annotate.h with
$(annotate_h).  Replace target.h with $(target_h).  Replace
gdbthread.h with $(gdb_thread_h).  Replace symfile.h with $(symfile_h).