[binutils-gdb] Constify some commands in symtab.c

[sergiodj+buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT 510e5e562796a5d2bbd4c7208155bd8a3c03b50d ***

Author: Tom Tromey <tom@tromey.com>
Branch: master
Commit: 510e5e562796a5d2bbd4c7208155bd8a3c03b50d

Constify some commands in symtab.c

gdb/ChangeLog
2017-09-27  Tom Tromey  <tom@tromey.com>

	* symtab.c (maintenance_print_symbol_cache)
	(maintenance_flush_symbol_cache)
	(maintenance_print_symbol_cache_statistics): Constify.