Patch for ABCL development versions

[Mark Evenson]

I'm unsure of the current ASDF work flow for patch submissions, but I
guessed that y'all would like [merge requests][57].

Without this patch, Elias' recent work on UIOP/RUN-PROGRAM won't be
utilized on any ABCL which is built from development source.

ABCL uses the convention that development versions start appending
strings separated via #\- characters to the primary value returned by
CL:LISP-IMPLEMENTATION-VERSION (e.g. '1.5.0-dev'. Such values cause the
UIOP/UTILITY:PARSE-VERSION function to return nil, meaning that this is
not a suitable conditional for whether LAUNCH-PROGRAM is invoked.

This patch uses the value of UIOP/OS:IMPLEMENTATION-IDENTIFIER to
identify version. Unknown whether this would work on MKCL/ECL, which
might simplify the code path here.

[57]: https://gitlab.common-lisp.net/asdf/asdf/merge_requests/57

Please let me know what I can do to conform to y'alls current style
conventions, test coverage, etc. for such a patch submission.  This
patch is necessary for [my backporting of Elias's work to JDK56][1]

[1]: http://abcl.org/trac/ticket/422

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