libc/glibc: normalize glibc hidden version names

Hidden version names for glibc conflicted:

LIBC_GLIBC_V_2.10.1
LIBC_V_2.10

name them constantly as:
LIBC_GLIBC_V_<version>

Reported-by: Esben Haabendal <eha@doredevelopment.dk>
Signed-off-by: Bryan Hundven <bryanhundven@gmail.com>

 reporter_name="Ioannis E. VENETIS"

 reporter_url="http://sourceware.org/ml/crossgcc/2009-11/msg00109.html"

 reporter_comment=""