Bug fix
Description:
pmake (on modi4, for instance) complains about undefined variables
if it is run without the -V flag, which turns those errors to warnings.
Solution:
Added test to configure.in to see if $MAKE will allow Makefiles
with undefined variables. If not, sets -V flag in AM_MAKEFLAGS.
Ensured that all custom make targets use AM_MAKEFLAGS.
Also defined all variables that caused errors in top-level Makefile.am.
This means that pmake can be used to build hdf5 *from the top level
only*. To run make from a subdirectory, still need to use -V flag
(or use make or gmake).
Platforms tested:
modi4, heping, copper, sleipnir
3f0a35a4ea
