Update GCC 4.7 and 4.8 bits/c++config.h to avoid inline namespace

Avoid using inline namespace not supported by GCC 4.2.

Without this, the test suite fails on ppc with error

 .../c++/4.8.2/ppc64-redhat-linux/bits/c++config.h:2019:
 error: expected unqualified-id before 'namespace'