-Wwrite-strings: More Solaris

-Wwrite-strings: More Solaris

Some obvious constifications found by attempting to build 64-bit GDB
on Solaris 11.

gdb/ChangeLog:
2017-04-05  Pedro Alves  <palves@redhat.com>

	* proc-api.c (struct trans): Constify.
	(procfs_note): Constify.
	* proc-events.c (struct trans, syscall_table):
	* proc-flags.c (struct trans): Constify.
	* proc-utils.h (procfs_note): Constify.
	* proc-why.c (struct trans): Constify.
	* procfs.c (dead_procinfo, find_syscall, proc_warn, proc_error)
	(procfs_detach): Constify.
	* sol-thread.c (struct string_map): Constify.
	(td_err_string, td_state_string): Constify.