Avoid "format not a string literal" warnings

Avoid "format not a string literal" warnings

On:

 $ uname -a
 NetBSD gcc70.fsffrance.org 5.1 NetBSD 5.1 (GENERIC) #0: Sat Nov  6 13:19:33 UTC 2010  builds@b6.netbsd.org:/home/builds/ab/netbsd-5-1-RELEASE/amd64/201011061943Z-obj/home/builds/ab/netbsd-5-1-RELEASE/src/sys/arch/amd64/compile/GENERIC amd64

With:

 $ g++ -v
 Using built-in specs.
 Target: x86_64--netbsd
 Configured with: /usr/src/tools/gcc/../../gnu/dist/gcc4/configure --enable-long-long --disable-multilib --enable-threads --disable-symvers --build=x86_64-unknown-netbsd4.99.72 --host=x86_64--netbsd --target=x86_64--netbsd --enable-__cxa_atexit
 Thread model: posix
 gcc version 4.1.3 20080704 prerelease (NetBSD nb2 20081120)

I saw:

 cc1plus: warnings being treated as errors
 ../../src/gdb/ctf.c: In function 'void ctf_save_metadata_header(trace_write_handler*)':
 ../../src/gdb/ctf.c:267: warning: format not a string literal, argument types not checked
 cc1plus: warnings being treated as errors
 ../../src/gdb/cli/cli-cmds.c: In function 'void alias_command(char*, int)':
 ../../src/gdb/cli/cli-cmds.c:1428: warning: format not a string literal and no format arguments
 ../../src/gdb/cli/cli-cmds.c:1457: warning: format not a string literal and no format arguments

gdb/ChangeLog:
2016-04-14  Pedro Alves  <palves@redhat.com>

	* cli/cli-cmds.c (alias_usage_error): New function.
	(alias_command): Use it.
	* ctf.c (ctf_save_metadata_header): Inline metadata_fmt local in
	ctf_save_write_metadata call.