wapiti uses sync_bool_compare_and_swap_8 on 32-bit archs where it is unavailable

[barracuda156]

--->  Configuring wapiti
--->  Building wapiti
Executing:  cd "/opt/local/var/macports/build/_opt_PPCSnowLeopardPorts_math_wapiti/wapiti/work/wapiti-1.5.0" && /usr/bin/make -j6 -w wapiti CC=/usr/bin/gcc-4.2 CFLAGS="-Os -std=c99 -arch ppc" 
make: Entering directory `/opt/local/var/macports/build/_opt_PPCSnowLeopardPorts_math_wapiti/wapiti/work/wapiti-1.5.0'
CC: wapiti.c --> wapiti
Undefined symbols:
  "___sync_bool_compare_and_swap_8", referenced from:
      _grd_subemp in cc370MXb.o
      _grd_subemp in cc370MXb.o
      _grd_spupgrad in cc370MXb.o
      _grd_spupgrad in cc370MXb.o
      _grd_flupgrad in cc370MXb.o
      _grd_flupgrad in cc370MXb.o
      _grd_domemm in cc370MXb.o
      _grd_domemm in cc370MXb.o
      _grd_domemm in cc370MXb.o
      _grd_domemm in cc370MXb.o
      _grd_domaxent in cc370MXb.o
      _grd_domaxent in cc370MXb.o
ld: symbol(s) not found
collect2: ld returned 1 exit status

It also needs to pass -std=c99, otherwise build fails immediately.