package/crosstool-ng: bumpimg default GCC version to 4.6.3

This bumps the GCC version from 4.4.6 to 4.6.3 to for
*.config-eglibc
*.config-glibc
*.config-uClibc
be equal to the default GCC setting in buildroot as well in addition to
commit b855154e.

Signed-off-by: Carsten Schoenert <c.schoenert@t-online.de>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>