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_64=y

 CT_ARCH_x86=y

 CT_KERNEL_windows=y

 CT_BINUTILS_V_2_21_1a=y

 CT_BINUTILS_PLUGINS=y

 CT_CC_V_4_5_2=y

 CT_CC_LANG_CXX=y

 CT_MINGW_DIRECTX=y

 CT_MINGW_DDK=y

 CT_GMP_V_4_3_2=y

 CT_MPFR_V_2_4_2=y

 CT_PPL_V_0_10_2=y

 CT_CLOOG_V_0_15_10=y