* gthr.h: Changed the comment about return values.
	* gthr-solaris.h (__gthread_once): Do not use errno; return the
	error number instead of -1.
	(__gthread_key_create): Any non-zero return value is an error.
	* libgcc2.c (eh_context_initialize): Check for non-zero return
	value from __gthread_once.
	Check that the value of get_eh_context was really changed.

From-SVN: r18480