hdf5_msb

[svn-r12306] Purpose:
Bug fix

Description:
Removed some extra compiler flags that were being added in configure

Solution:
After my previous changes, some of autoconf's macros were realizing that
we had no CFLAGS defined and were helpfully supplying some to us, which
were causing errors on some platforms.
Initializing all of the *FLAGS variables prevented this from happening.

Platforms tested:
mir (minor change)