Support all in gdb goroutine commands.

For example, can use `goroutine all bt` to dump all goroutines
infomation.

src/runtime/runtime-gdb.py

@@ -518,6 +518,19 @@ def __init__(self):
 		gdb.Command.__init__(self, "goroutine", gdb.COMMAND_STACK, gdb.COMPLETE_NONE)
 
 	def invoke(self, arg, _from_tty):
+		goid_str, cmd = arg.split(None, 1)
+		goids = []
+
+		if goid_str == 'all':
+			for ptr in SliceValue(gdb.parse_and_eval("'runtime.allgs'")):
+				goids.append(int(ptr['goid']))
+		else:
+			goids = [int(gdb.parse_and_eval(goid_str))]
+
+		for goid in goids:
+			self._invoke(goid, cmd)
+
+	def _invoke(self, goid, cmd):
 		goid, cmd = arg.split(None, 1)
 		goid = gdb.parse_and_eval(goid)
 		pc, sp = find_goroutine(int(goid))