For PR1256:

Make Signedness information pervasive throughout all types and values.
There is no easy way to get around this. Because the GEP instruction can
index through an arbitrarily complex value structure, it is necessary to
keep track of signedness information throughout that structure. This change
makes Signedness a full class, capable of representing Signedness in
arbitrarily shaped types. The class is then used throughout llvm-upgrade to
track signedness and differentiate between globals, locals, and functions
based on their signedness.

For PR1243:
This patch also removes bogus warnings about renaming internal globals. It
now only emits such warnings when renaming non-internal globals because
they may affect linkage.

llvm-svn: 35234