* solib.c (BKPT_AT_MAIN): Change to BKPT_AT_SYMBOL.

	* solib.c (BKPT_AT_MAIN):  Change to BKPT_AT_SYMBOL.
	* solib.c (bkpt_names):  New array of symbol names to try to
	use for the "mapping complete" breakpoint.  Configurable
	define SOLIB_BKPT_NAME is first one to try.
	* solib.c (find_solib):  Test debug_base for nonzero rather
	than just greater than zero.
	* solib.c (enable_break):  Use bkpt_names to look up address
	at which to set "mapping complete" breakpoint.