Improvement
Description:
If $CXX is not defined, configure will try a list of possible
C++ compiler name. That is not always desireable.
Solution:
Change configure to combine all powerpc-ibm-aix* to one version.
Add xlC as the default $CXX value.
Platforms tested:
Tested in Copper only since the change affect AIX machine only.
Misc. update:
