Fix PowerPC Mac build
Make LONG 32 bits for ppc64 as it is for x86_64
Add ppc optimization for clz and fixmul

Optimize ppc/ppc64 similar to i386/x86_64, approximately doubling
encoding speed on a Power Mac G5 running OS X 10.5.8.
Fix AIX build

Fix AIX build failure with IBM xlC compiler due to conflicting
definition of M_PI.  The libSYS/include/genericStds.h definition is
guarded with #ifndef M_PI, but was included before <math.h> which
defines M_PI with more significant digits.