Update r23747 -- require 2.0.10 for guile2 builds, but allow older versions
for guile 1.8 builds.  However if we don't have guile 2.0.10 then don't
allow "make dist" to run.  This also means we wont patch the guile
files unless we find swig 2.0.10.

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@23748 57a11ea4-9604-0410-9ed3-97b8803252fd