[MOAB-dev] Error configuring MOAB with PG compiler

[Jason Kraftcheck]

Robert Smith wrote:
> It seems that during configure the tests for HDF5 use the '-isystem'
> flag to add the HDF5 include directory to the system include path.
> 
> This flag is not supported by pgcc and so all tests fail.  This causes
> configure to fail.
> 
> Is this a problem in the configure input files?
> 

This flag was only added if the C++ compiler was g++.  I changed it such
that both compilers (C++ and C) must be GNU before the flag is used.
Hopefully this fixes the above issue.

- jason