fix plex bug

The get external definitions routine that operates on the users cpp file
was tripped by the "friend class foo" statement because it thought it
was an aggregate fwd declaration.

The only way to trigger was to have two different classes declare the
same friend, so we hit that __debugbreak();
non change on vcxproj

sucks ass that reformated the line. its a no-op
adding plx::ReaderWriterLock

a wrapper of a slim rwl of windows.