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>

 # MicroBlaze specific config options

 ## depends on EXPERIMENTAL

 ##

 ## select ARCH_SUPPORT_ARCH

 ## select ARCH_FLOAT_SW

 ## select ARCH_SUPPORTS_BOTH_ENDIAN

 ## select ARCH_DEFAULT_BE

 ## select ARCH_SUPPORTS_BOTH_MMU

 ## select ARCH_DEFAULT_HAS_MMU

 ##

 ## help The MicroBlaze architecture, as defined by:

 ## help 	http://www.xilinx.com/

 ## help 

 ## help Upstream projects do not currently provide

 ## help full support for the microblaze architecture

 ## help and as such, this is marked as EXPERIMENTAL

 ## help for CT-NG.

 ## help 

 ## help Support is being added for a modern gcc,

 ## help binutils and gdb along with nptl threading

 ## help in eglibc for microblaze.