fix library name for mpich 3.1.1+ cxx builds

ChangeLog

@@ -25,8 +25,8 @@ darshan-2.3.1-pre2
   - label I/O vs. meta time more clearly
   - include unique file meta time in agg_perf_by_slowest calculation
 * added regression test script framework in darshan-test/regression/
-* update darshan-gen-fortran.pl to support new Fortran library name in 
-  MPICH 3.1.1
+* update darshan-gen-fortran.pl and darshan-gen-cxx.pl to support new library
+  naming conventions in MPICH 3.1.1 and higher
 
 darshan-2.3.0
 =============

darshan-runtime/darshan-gen-cxx.pl.in

@@ -274,10 +274,14 @@ print OUTPUT<<"EOF";
     if [ \$? -eq 0 ] ; then
         CXXMPICH=-lcxxmpich
     fi
-    grep -E cxxmpich\\.cnk.a \$tmpfile >& /dev/null
+    grep -E cxxmpich\\.cnk\\.a \$tmpfile >& /dev/null
     if [ \$? -eq 0 ] ; then
         CXXMPICH=-lcxxmpich.cnk
     fi
+    grep -E mpicxx\\.a \$tmpfile >& /dev/null
+    if [ \$? -eq 0 ] ; then
+        CXXMPICH=-lmpicxx
+    fi
 
     rm \$tmpfile >& /dev/null