fixed compiling on AIX 6.1

using gcc on aix fail because of -Wall if not using -fwrapv, probably issue optimization
Should think about using -brtl for linking in future (maybe)
# gcc -v
Using built-in specs.
Target: powerpc-ibm-aix6.1.0.0
Configured with: ../configure --with-as=/usr/bin/as --with-ld=/usr/bin/ld --enable-languages=c,c++,java --prefix=/opt/freeware --enable-threads --enable-version-specific-runtime-libs --host=powerpc-ibm-aix6.1.0.0 --target=powerpc-ibm-aix6.1.0.0 --build=powerpc-ibm-aix6.1.0.0 --disable-libjava-multilib
Thread model: aix
gcc version 4.2.0