Properly use the b.eq/b.ge forms instead of the nonstandard forms
(which both gas and newer clang accept though), and expand the
register list that used a range (which the Xcode 6.2 clang, based
on clang 3.5 svn, didn't support).

This is cherrypicked from libav commit
a970f9de.
Signed-off-by: Martin Storsjö <martin@martin.st>