arch: allow adding a suffix to the arch-part of a tuple

For some architectures, it is legit to have an alternate value in the
'architecture' part of the tuple. For example:
armv5te-*
armv7a8-*

Besides, some packages expect the tuple to reflect the arch variant
(eg. openMPI) to detect the variant's capabilities (eg. atomic
primitives).

This patch adds an option for the user to specify a suffix to be added
to the arch-part of the tuple.

Signed-off-by: Willy Tarreau <w@1wt.eu>
Message-ID: <20130120225822.GS6838@1wt.eu>
Patch-Id: 213994
[yann.morin.1998@free.fr: make it a suffix, not an override]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

 CT_EXPERIMENTAL=y

 CT_LOCAL_TARBALLS_DIR="${HOME}/src"

 CT_SAVE_TARBALLS=y

 CT_LOG_EXTRA=y

 CT_ARCH_CPU="ev56"

 CT_ARCH_TUNE="ev56"

 CT_ARCH_ALPHA_EV67=y

 CT_KERNEL_linux=y

 CT_KERNEL_V_2_6_38_8=y

 CT_BINUTILS_V_2_21_1a=y

 CT_CC_V_4_3_5=y

 CT_CC_LANG_FORTRAN=y

 CT_CC_LANG_CXX=y

 # CT_CC_GCC_ENABLE_TARGET_OPTSPACE is not set

 CT_LIBC_glibc=y

 CT_LIBC_GLIBC_V_2_13=y

 CT_LIBC_EXTRA_CC_ARGS="-Wl,--no-relax"

 CT_LIBC_GLIBC_USE_PORTS=y

 CT_GMP_V_5_0_1=y

 CT_MPFR_V_3_0_0=y