For Sunos 4.x targets, enable gdb to set breakpoints in shared

	For Sunos 4.x targets, enable gdb to set breakpoints in shared
	library functions before the executable is run. Retrieve dynamic
	symbols from stripped executables.
	* symtab.h (minimal_symbol_type):  Add mst_solib_trampoline type.
	* parse.c (write_exp_msymbol), symmisc.c (dump_msymbols),
	symtab.c (list_symbols):  Handle mst_solib_trampoline.
	* minsyms.c (lookup_minimal_symbol):  Handle mst_solib_trampoline
	for all targets, remove IBM6000_TARGET dependencies.
	* dbxread.c (read_dbx_dynamic_symtab):  New function.
	* dbxread.c (dbx_symfile_read):  Use it.
	* dbxread.c (SET_NAMESTRING):  Set namestring to
	"<bad string table index>" instead of "foo" if the string index is
	corrupt.
	* xcoffread.c (read_xcoff_symtab):  Use mst_solib_trampoline instead
	of mst_unknown.
	* symtab.c (list_symbols):  Take from_tty as parameter and pass it
	to break_command. Handle mst_file_* minimal symbol types.