Docs: fix some wrong words (GH-6987)

Fix typos in code comments: bdb.py and configure.ac.

Lib/bdb.py

@@ -257,7 +257,7 @@ class Bdb:
         pass
 
     def user_line(self, frame):
-        """Called when when we stop or break at a line."""
+        """Called when we stop or break at a line."""
         pass
 
     def user_return(self, frame, return_value):

configure.ac

@@ -153,7 +153,7 @@ AC_ARG_ENABLE(universalsdk,
 [
 	case $enableval in
 	yes)
-		# Locate the best usable SDK, see Mac/README.txt for more
+		# Locate the best usable SDK, see Mac/README for more
 		# information
 		enableval="`/usr/bin/xcodebuild -version -sdk macosx Path 2>/dev/null`"
 		if ! ( echo $enableval | grep -E '\.sdk' 1>/dev/null )
@@ -572,7 +572,7 @@ fi
 if test "$ac_sys_system" = "Darwin"
 then
 	# Compiler selection on MacOSX is more complicated than
-	# AC_PROG_CC can handle, see Mac/README.txt for more
+	# AC_PROG_CC can handle, see Mac/README for more
 	# information
 	if test -z "${CC}"
 	then