Add check for winsock2.h for socket.h replancement. Also, use this
check to add ws2_32 library. Also, switch all winsock.h references
to winsock2.h.

Add check for getuid and getpass; which are not on mingw.

Add a syslog() replacement that is basically a print(). This
is also used by vsyslog() replacement.

Comment out parts of replacement sigprocmask.c on mingw.

To support these configure.in changes, I need to rebuild all
related files with autoconf 2.68 and libtool 2.4. Hand ported
our sane-backend specific changes to newer ltmain.sh.