hdf5

[svn-r19470] Bug fix: 1961-- AIX 6.1 --enable-share did not work.

Description:
In an AIX 6.1 system, configure --enable-shared could not build a shared
HDF5 library. The problem was because the version of config.guess was too
old to recongnize AIX 6.X and also configure.in had a local fix which did
not recognize AIX 6.X.

Solution:
1. Mike McGreevy updated bin/config.guess to handle AIX 6.X.
2 Albert fixed configure.in to recognize AIX 6.X.

Note that though HDF5 can build shared lib for AIX 6.X systems
but it still could not install the proper library as in AIX 5.X
systems. Also, bin/config.sub should be updated too.

Tested: BP which is the AIX 6.1 system that exposed this problem.