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>

This is a somewhat ordered TODO list:

Recurring tasks:

- update versions for every tools...

- update and/or upgrade all samples

Non-recurring tasks:

- update newlib (for enhanced bare metal)

  - confirm existing implementation on targets other than AVR32

  - try to make it generic, will help for uClibc++

- multilib

- Cygwin target (needs newlib)

  - so we can build toolchains that generate code for Windows/Cygwin

- Cygwin host

  - so we can build toolchains that run natively under Windows/Cygwin

- mingw32 target

  - so we can build toolchains that generate code for Windows/Win32

- mingw32 host

  - so we can build toolchains that run natively under Windows/Win32

    (without requiring Cygwin)

- uClibc++

  - see newlib, above

- uClinux

  - check whether we can use newlib under uClinux (?)