[binutils-gdb] Use gdbarch obstack to allocate the TYPE_NAME string in arch_type

[sergiodj+buildbot at redhat dot com]

*** TEST RESULTS FOR COMMIT aa78b3b28aeff4bb9977a313f5a8002d920b34c5 ***

Author: Patrick Palka <patrick@parcs.ath.cx>
Branch: master
Commit: aa78b3b28aeff4bb9977a313f5a8002d920b34c5

Use gdbarch obstack to allocate the TYPE_NAME string in arch_type

Since the type whose name is being set is now being allocated on the
gdbarch obstack, we should allocate its TYPE_NAME on the obstack too.
This reduces the number of individual valgrind warnings for the command
"gdb gdb" from ~300 to ~150.

Tested on x86_64-unknown-linux-gnu.

gdb/ChangeLog:

	* gdbarch.h (gdbarch_obstack_strdup): Declare.
	* gdbarch.c (gdbarch_obstack_strdup): Define.
	* gdbtypes.c (arch_type): Use it.