[llvm-pdbdump] Add include-only filters.

PDB files have a lot of noise in them, with hundreds (or thousands)
of symbols from system libraries and compiler generated types.  If
you're only looking for a specific type, this can be problematic.

This CL allows you to display *only* types, variables, or compilands
matching a particular pattern.  These filters can even be combined
with exclude filters.  Include-only filters are given priority, so
that first the set of items to display is limited only to those that
match the include filters, and then the set of exclude filters is
applied to those.  If there are no include filters specified, then
it means "display everything".

llvm-svn: 248822