cc/gcc: add language helper function

Add a function that prepares the language configure option.
It is needed in at least two places, some commonalisation is needed. ;-)

Unfortunately, it is no longer possible to print warnings about experimental
languages any more. Anyway, the experimental status is clearly indicated
in the menuconfig. so it should not be a surprise if the build breaks. :-/

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

 This is NOT the official version of dialog.  This version has been

 significantly modified from the original.  It is for use by the Linux

 kernel configuration script.  Please do not bother Savio Lam with 

 questions about this program.