Rename pprof to jeprof.

This rename avoids installation collisions with the upstream gperftools.
Additionally, jemalloc's per thread heap profile functionality
introduced an incompatible file format, so it's now worthwhile to
clearly distinguish jemalloc's version of this script from the upstream
version.

This resolves #229.
diff --git a/ChangeLog b/ChangeLog
index 6f79cac..33139f9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -117,8 +117,9 @@
   - Assure that the constness of malloc_usable_size()'s return type matches that
     of the system implementation.
   - Change the heap profile dump format to support per thread heap profiling,
-    and enhance pprof with the --thread=<n> option.  As a result, the bundled
-    pprof must now be used rather than the upstream (gperftools) pprof.
+    rename pprof to jeprof, and enhance it with the --thread=<n> option.  As a
+    result, the bundled jeprof must now be used rather than the upstream
+    (gperftools) pprof.
   - Disable "opt.prof_final" by default, in order to avoid atexit(3), which can
     internally deadlock on some platforms.
   - Change the "arenas.nlruns" mallctl type from size_t to unsigned.