Log Message:
Update to 1.9.15 and switch to guile20

This package had been held at 1.9.14 because 1.9.15 requires guile
2.0.

Changes from 1.9.14:

  G-Wrap now requires Guile 2.0, allows Guile 2.2;

  Requires autoconf >= 2.61, automake >= 1.12, adding /build-aux

  We no longer update Changelog, see G-Wrap's git logs instead

  No free/mark on WCT objects, and remove use of scm_gc_free

  Use scm_module_variable instead of the deprecated scm_sym2var

  The documentation has been restructured, updated and fixed to work with \ 
texinfo >= 5.2;

  Removing doc/version.texi - it is generated/updated