bug#33675: configure fails when both guile 2.2 and 2.0 are installed

[Tommi Höynälänmaa]

Script configure gives the following errors when both guile 2.2 and 2.0 
are installed:
---cut here---
checking for guile-2.0.14... no
checking for guile2.0.14... no
checking for guile-2.0... /usr/bin/guile-2.0
configure: error: found development files for Guile 2.2, but 
/usr/bin/guile-2.0 has effective version 2.0
---cut here---
I use guile versions 2.0.13 and 2.2.4 on Debian testing.

     - Tommi Höynälänmaa