update docs and changelog

ChangeLog

@@ -10,6 +10,11 @@ Darshan-3.1.3-pre1
 * skip instrumentation attempts for anonymous mmap() calls; this avoids a
   potentential deadlock condition when used with hugepages on Cray systems.
   Reported by Glenn Lockwood and Cristian Simarro.
+* disable HDF5 module by default unless enabled using --enable-HDF5-post-1.10
+  or --enable-HDF5-pre-1.10 configure arguments.  These options
+  vary the wrapper prototypes to match the corresponding HDF5 library ABI.
+  The initial patch for HDF5 1.10 compatibility was contributed by 
+  Karl-Ulrich Bamberg.
 
 Darshan-3.1.2
 =============

darshan-runtime/doc/darshan-runtime.txt

@@ -76,6 +76,10 @@ header and library.
 and only builds if BG/Q environment detected).
 * `--enable-group-readable-logs`: sets darshan log file permissions to allow
 group read access.
+* `--enable-HDF5-pre-1.10`: enables the Darshan HDF5 instrumentation module,
+with support for HDF5 versions prior to 1.10
+* `--enable-HDF5-post-1.10`: enables the Darshan HDF5 instrumentation module,
+with support for HDF5 versions 1.10 or higher
 
 === Cross compilation