complibs: remove experimental from versions selection

Since I removed EXPERIMENTAL to most of gcc versions, the configuration
is now broken, as the required companion libraries versions are not
selectable, as they are still hidden behind EXPERIMENTAL.

Reported-by: Claudio Henrique Fortes Felix (chffelix on irc://irc.freenode.net/crosstool-ng)
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

 reporter_name="Kevin Cernekee"

 reporter_url="http://sourceware.org/ml/crossgcc/2011-09/msg00037.html"

 reporter_comment="MIPS SDE-compatible toolchain"