Fix hang when building libgpg-error.
Build glib-networking (required by libsoup) in gnutls.

Ensure that its version is coordinated with glib's by using new variable
GLIB_VERSION for both.
Fix up libgnutls installation when building from source.

We don't actually build libgnutls from source, so we need to create the
directory for it. The .la files it provides contain the builder's paths
which screws up libtool later, so delete them.
Get rid of some of the libfoo.la has moved warnings.

The warning is caused by finding the libtool-lib on a different path than
the one encoded in its libdir statement; it's a purely lexical check,
so if the mingw version, /c/gcdev is given in the -L directive and c:/gcdev
is in the libdir statement, libtool will issue the warning.

The only one remaining is libintl, which is usually found with /c/gcdev/mingw/lib
but whose libdir=/mingw.
Unfortunately just about every other library links to this so it's issued
a lot.