bug#64723: [PATCH] Improve DLL search strategy for load-foreign-library

[Mike Gran]

> The new non-libltdl foreign library loading algorithm from 3.0.6
> fails to cover common cases regarding how libtool names and installs
> DLL files.  Notably, it fails to recognize when libtool has added the
> major version number into the filename itself, such as libfoo-1.dll
> Also, it does not search in binary directories and the PATH for DLL
> files, where libtool is likely to install DLLs.

Hi All-

This is the first of a dozen patches to make Win32 minimally viable
again. This patch specifically removes a regression introduced in 3.0.6
described above.

If I hear no objection, I'm going to rebase and push
in a week or two.

There are only a couple things in here to which one might find
interesting (aka objectionable).  One is the renaming of the 
"#:rename-on-cygwin?
option of `load-foreign-library` to "#:host-type-rename?" to
indicate that it handles both msys and cygwin libraries.

The other is the code itself, which could be a lot shorter
if I pulled in other modules. I'm
never comfortable pulling in modules into other modules in
Guile's core itself, for fear of creating spaghetti.  As a consequence,
some of the string handling is comically verbose.

Regards,
Mike Gran