tweak autoconf help language

darshan-runtime/configure

@@ -1322,7 +1322,7 @@ Optional Features:
   --disable-cuserid       Disables attempted use of cuserid() at run time
   --enable-group-readable-logs
                           Set log files to be group readable
-  --enable-HDF5_1.10       Compile for use with HDF5 1.10.x
+  --enable-HDF5_1.10      Enable explicit support for HDF5 1.10.x API
   --disable-bgq-mod       Disables compilation and use of BG/Q module (for BG/Q systems)
   --disable-lustre-mod    Disables compilation and use of the Lustre module
   --enable-mmap-logs      Enables ability to mmap I/O data to log file

darshan-runtime/configure.in

@@ -47,9 +47,9 @@ fi]
 ,)
 
 AC_ARG_ENABLE(HDF5_1.10,
-[  --enable-HDF5_1.10       Compile for use with HDF5 1.10.x],
+[  --enable-HDF5_1.10      Enable explicit support for HDF5 1.10.x API],
 [if test "x$enableval" = "xyes" ; then
-    AC_DEFINE(__DARSHAN_ENABLE_HDF5110, 1, Set for compatibility with HDF5_1.10.x, breaks use with 1.8.x)
+    AC_DEFINE(__DARSHAN_ENABLE_HDF5110, 1, Explicitly enable HDF5_1.10.x support, will break 1.8.x compatibility on 32bit platforms)
 fi]
 ,)
 

darshan-runtime/darshan-runtime-config.h.in

@@ -87,7 +87,7 @@
 /* Define if cuserid() should be disabled */
 #undef __DARSHAN_DISABLE_CUSERID
 
-/* Set for compatibility with HDF5_1.10.x */
+/* Explicitly enable HDF5_1.10.x support */
 #undef __DARSHAN_ENABLE_HDF5110
 
 /* Define if Darshan should mmap data structures to log file */