src: rewrite symfile sorting checker in Python

As part of a goal to eliminate Perl from libvirt build tools,
rewrite the check-symsorting.pl tool in Python.

This was a straight conversion, manually going line-by-line to
change the syntax from Perl to Python. Thus the overall structure
of the file and approach is the same.

Tested-by: Cole Robinson <crobinso@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

Makefile.am

@@ -48,6 +48,7 @@ EXTRA_DIST = \
   scripts/augeas-gentest.py \
   build-aux/check-spacing.pl \
   scripts/check-aclperms.py \
+  scripts/check-symsorting.py \
   scripts/header-ifdef.py \
   scripts/minimize-po.py \
   scripts/mock-noinline.py \