First part of changes to eliminate problems with cv-qualifiers and

sugared types. The basic problem is that our qualifier accessors
(getQualifiers, getCVRQualifiers, isConstQualified, etc.) only look at
the current QualType and not at any qualifiers that come from sugared
types, meaning that we won't see these qualifiers through, e.g.,
typedefs:

  typedef const int CInt;
  typedef CInt Self;

Self.isConstQualified() currently returns false!

Various bugs (e.g., PR5383) have cropped up all over the front end due
to such problems. I'm addressing this problem by splitting each
qualifier accessor into two versions: 

  - the "local" version only returns qualifiers on this particular
    QualType instance
  - the "normal" version that will eventually combine qualifiers from this
    QualType instance with the qualifiers on the canonical type to
    produce the full set of qualifiers.

This commit adds the local versions and switches a few callers from
the "normal" version (e.g., isConstQualified) over to the "local"
version (e.g., isLocalConstQualified) when that is the right thing to
do, e.g., because we're printing or serializing the qualifiers. Also,
switch a bunch of
  
  Context.getCanonicalType(T1).getUnqualifiedType() == Context.getCanonicalType(T2).getQualifiedType()

expressions over to 

  Context.hasSameUnqualifiedType(T1, T2)

llvm-svn: 88969