Fix _nl_find_msg malloc failure case, and callers.

This patch fixes two issues, and perhaps should be two distinct commits,
but I present it here as one for the sake of completeness.

Commit 006dd86111c44572dbd3b26e9c63dd0f834d7762 fails to check malloc's
return in intl/dcigettext.c (_nl_find_msg):
~~~
      freemem_size = INITIAL_BLOCK_SIZE;
      newmem = (transmem_block_t *) malloc (freemem_size);
...
      newmem->next = transmem_list;
      transmem_list = newmem;
~~~
If malloc fails then newmem is NULL then newmem->next results in a
fault.

The fix is easy enough, check for newmem != NULL, and fall through to
the error condition below which returns (char *) -1 e.g. resource error.

The problem is that returning (char *) -1  will break all sorts of other
code, so while what we did is correct, the real failure case fix is
slightly broader.

There are 4 other places where _nl_find_msg is called, one is OK, the
other three are fixed to handle -1 error return value.

No regressions on x86-64 or x86.

However, no regressions isn't really a useful metric for this code.

The change was tested as documented here:
http://sourceware.org/glibc/wiki/Testing/WhiteBox
using SystemTap for fault injection to simulate malloc failure.

---

2013-05-03  Carlos O'Donell  <carlos at redhat.com>

	[BZ #15441]
	* intl/dcigettext.c (DCIGETTEXT): Skip translating if _nl_find_msg
	returns -1.
	(_nl_find_msg): Return -1 if recursive call returned -1. If newmem is
	null return -1.
	* intl/loadmsgcat.c (_nl_load_domain): If _nl_find_msg returns -1 abort
	loading the domain.