cc/gcc: remove 'sub-level' version form symbols

Now we use defconfig files to store the samples, we have to be a bit more
conservatives in the symbols names, so as to avoid gigantic version bumps
when updating sub-level versions from a package.

For example (using fictitious versions):
- in crosstool-NG 1.17.0, we choose:
- latest gcc is gcc-linaro-4.7-2012.10, which is the default for the
choice in the menuconfig
- gcc-linaro-4.6-2012.10 is selected
- so, sample has an explicit symbol for the selected gcc version, as it
is not the default
- we update to crosstool-NG 1.18.0:
- latest gcc version is gcc-linaro-4.7-2013.01
- gcc-linaro-46 has been updated to gcc-linaro-4.6-2013.01
- as the sample now has no *valid* symbol to set the gcc version, the
default is used, while we would have expected to still use the 4.6
release from linaro, not the 4.7

Get rid of sub-level (ie. the third digit sequence in versions) from the
symbols for linaro versions.

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

 # Compute powerpc-specific values

 CT_DoArchTupleValues () {

     # The architecture part of the tuple, override only for 64-bit

     if [ "${CT_ARCH_64}" = "y" ]; then

         CT_TARGET_ARCH="powerpc64${CT_ARCH_SUFFIX}"

     fi

     # Only override values when ABI is not the default

     case "${CT_ARCH_powerpc_ABI}" in

         eabi)

             # EABI is only for bare-metal, so libc ∈ [none,newlib]

             CT_TARGET_SYS="eabi"

             ;;

         spe)

             case "${CT_LIBC}" in

                 none|newlib)    CT_TARGET_SYS="spe";;

                 *glibc)         CT_TARGET_SYS="gnuspe";;

                 uClibc)         CT_TARGET_SYS="uclibcgnuspe";;

             esac

             ;;

     esac

     # Add extra flags for SPE if needed

     if [ "${CT_ARCH_powerpc_ABI_SPE}" = "y" ]; then

         CT_ARCH_TARGET_CFLAGS="-mabi=spe -mspe"

         CT_ARCH_CC_CORE_EXTRA_CONFIG="--enable-e500_double"

         CT_ARCH_CC_EXTRA_CONFIG="--enable-e500_double"

     fi

 }