Update Win32 builds to mostly work under Cygwin.

Update Win32 builds to mostly work under Cygwin.

Makefile.win32: Add -mno-cygwin to LDFLAGS so native Cygwin builds work.
configure.in: Look for stdint.h, localtime() and --with-win32.
src/compat.c: Remove "extern" modifiers on function definitions. Only
  implement localtime_r() if we have localtime() too.
src/compat.h: Include stdint.h if we have it; define LINE_MAX if needed.
  Also define NI_NUMERICHOST for the benefits of getnameinfo().
src/config.h.win32: Resynchronize with config.h.in; set WITH_IOSET_SELECT
  and WITH_PROTOCOL_P10.