Win32: properly enabled select on Windows.

Win32: properly enabled select on Windows.

Previously, select was compiled in by default, but the NGX_HAVE_SELECT
macro was not set, resulting in iocp being used by default unless
the "--with-select_module" configure option was explicitly specified.
Since the iocp module is not finished and does not work properly, this
effectively meant that the "--with-select_module" option was mandatory.

With the change NGX_HAVE_SELECT is properly set, making "--with-select_module"
optional.  Accordingly, it is removed from misc/GNUmakefile win32 target.