configure: fix version string breakage

As we use the directory names as Makefile targets, they can not contain any
column ':', or else make will complain about 'multiple target patterns'.

Replace the offending ':' with a dash '-', as Titus suggested.

Reported-by: Erdem Budak <erdembudak@hotmail.com>
Reported-by: Titus von Boxberg <titus@v9g.de>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

 # Default test suite configuration

 # Default DejaGnu configuration

 DG_TOOLNAME = gcc

 DG_TARGET_HOSTNAME = 127.0.0.1

 DG_TARGET_USERNAME = root

 # Default tests

 DG_C_TESTS = 

 DG_CPP_TESTS =