Fix PR16220

Fix PR16220

This patch removes startup_gdbarch because it is not used anymore.
After this patch,

 [PATCH] Multi-process + multi-arch: GDB
 https://sourceware.org/ml/gdb-patches/2012-11/msg00228.html

global variable target_gdbarch is removed and gdbarch becomes
per-inferior.  Then, we don't have to keep global variable
startup_gdbarch.

Rebuild GDB with all targets.  Is it OK?

gdb:

2014-02-18  Yao Qi  <yao@codesourcery.com>

	PR gdb/16220
	* gdbarch.sh: Remove startup_gdbarch.
	* gdbarch.c: Regenerated.
	* gdbarch.h: Likewise.