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.

src/prof.c

@@ -1418,7 +1418,7 @@ prof_leakcheck(const prof_cnt_t *cnt_all, size_t leak_ngctx,
 		    cnt_all->curobjs, (cnt_all->curobjs != 1) ? "s" : "",
 		    leak_ngctx, (leak_ngctx != 1) ? "s" : "");
 		malloc_printf(
-		    "<jemalloc>: Run pprof on \"%s\" for leak detail\n",
+		    "<jemalloc>: Run jeprof on \"%s\" for leak detail\n",
 		    filename);
 	}
 }