scripts/functions: introduce target_bits_32 and target_bits_64 variables

These variables behave the same for bitness as their counterparts do
for endianness: they are defined to the appropriate bitness.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Cody P Schafer <dev@codyps.com>

CT_LOCAL_TARBALLS_DIR="${HOME}/src"

CT_SAVE_TARBALLS=y

CT_CONFIG_SHELL_SH=y

CT_LOG_EXTRA=y

CT_ARCH_avr32=y

CT_BINUTILS_V_2_18a=y

CT_CC_V_4_2_2=y

CT_LIBC_NEWLIB_V_1_17_0=y

CT_LIBC_NEWLIB_IO_LL=y

CT_LIBC_NEWLIB_IO_FLOAT=y

CT_LIBC_NEWLIB_DISABLE_SUPPLIED_SYSCALLS=y