compiler.

Issue 9174.

This introduces a 'purge' function for the fnmatch module analogous
to the 'purge' function in the re module.

Silence gcc warning. (In function 'bytearray_init': warning: 'value' may be used uninitialized in this function).

configure to append to Python's default values for those variables, and
similarly allow users to set $XXFLAGS on the make command line to append to the
values set by configure.

In the makefile, this renames the variables that used to be $XXFLAGS to
$PY_XXFLAGS, and renames the old $PY_CFLAGS to $PY_CORE_CFLAGS.  To compensate,
sysconfig now aliases $XXFLAGS=$PY_XXFLAGS so that scripts using it keep
working.  I see that as the right interface, not a backward-compatibility hack,
since these are logically the $XXFLAGS variables; we just use a different name
in the makefile to deal with make's semantics.

with a few minor touchups.

using WindowsError in a try/except. Only add WindowsError to the list of
exceptions to catch when we are actually running on Windows.

Additionally, add a call that was left out in test_posixpath.

Thanks Amaury, Antoine, and Jason.