[svn-r7248] Purpose:

Bug fix

Description:
The "prefix?=..." is not recognized by all make commands.  Even some
older gmake do not recognize it.  The result is that "make install"
failed for many platforms (AIX, Solaris 2.7, HPUX 11, ...) because
when they tried to install at $(prefix)/lib, it becomes /lib since
$(prefix) is not defined.


Solution:
Restore it back to the previous
   prefix=...


Platforms tested:
h5committested.
Also ran in-place build using vendor make in kelgia, arabica
and copper.

Misc. update:

config/commence.in

@@ -34,7 +34,7 @@ RUNTEST=$(RUNSERIAL)
 TRACE=:
 
 ## Installation points
-prefix?=@prefix@
+prefix=@prefix@
 exec_prefix=@exec_prefix@
 bindir=@bindir@
 libdir=@libdir@