Deprecate function `haveRtldLocal`

The function haveRtldLocal was introduced for compatibility with Cygwin
on Mar 28 2002 in GHC commit 4740cf56c774b92e02d31b4666158d70c2e85a8f.

According to https://cygwin.com/viewvc/src/winsup/cygwin/include/dlfcn.h
RTLD_LOCAL has been available on Cygwin since Revision 1.4 (August 9 2010).