Change the return types of ctz, clz and popcount

[Reviewed by Elliot]

After this change clz, ctz and popcount will return the same integer type they
take in. The motivation behind this was to make the return values easier to
work wtih. The prototypes in chpl-bitops.h have been changed to match that of
the underlying intrinsic.


git-svn-id: http://svn.code.sf.net/p/chapel/code/trunk@23818 3a8e244f-b0f2-452b-bcba-4c88e055c3ca
Add .good for no-op test.

Thought I added one but clearly I didn't.


git-svn-id: http://svn.code.sf.net/p/chapel/code/trunk@23819 3a8e244f-b0f2-452b-bcba-4c88e055c3ca