Add missing comma for --enable-werror.
Remove broken signal handler on cygwin.

SA_SIGINFO is not supported properly on cygwin ATM.
according to _cygtls::call_signal_handler() in winsup/cygwin/exception.cc,
the the 3rd argument of signal handler is NULL even if SA_SIGINFO was set.
http://cygwin.com/cgi-bin/cvsweb.cgi/src/winsup/cygwin/exceptions.cc?rev=1.432&content-type=text/x-cvsweb-markup&cvsroot=src

FYI, following code project looks promising, but we need to fix cygwin
itself.
http://www.codeproject.com/Articles/4225/Unix-ucontext_t-Operations-on-Windows-Platforms
Merge pull request #27 from hiyuh/nosignal

NO_STACK_TRACE for cygwin