Issue #18080: When building a C extension module on OS X, if the compiler
is overriden with the CC environment variable, use the new compiler as
the default for linking if LDSHARED is not also overriden.  This restores
Distutils behavior introduced in 2.7.3 and inadvertently dropped in 2.7.4.
#17403: urllib.parse.robotparser normalizes the urls before adding to ruleline.
This helps in handling certain types invalid urls in a conservative manner.