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>

 # powerpc specific configuration file

 ## select ARCH_SUPPORTS_32

 ## select ARCH_SUPPORTS_64 if EXPERIMENTAL

 ## select ARCH_DEFAULT_32

 ## select ARCH_USE_MMU

 ## select ARCH_SUPPORT_ABI

 ## select ARCH_SUPPORT_CPU

 ## select ARCH_SUPPORT_TUNE

 ##

 ## help The PowerPC architecture, as defined by:

 ## help     http://www.ibm.com/developerworks/eserver/articles/archguide.html