setup.py: package internals help files

mpm says internal docs should be visible via `hg help` and hgweb. They
need to be in the distribution for this to work. Package them.

setup.py

@@ -591,6 +591,7 b' except ImportError:'
 
 packagedata = {'mercurial': ['locale/*/LC_MESSAGES/hg.mo',
                              'help/*.txt',
+                             'help/internals/*.txt',
                              'default.d/*.rc',
                              'dummycert.pem']}