Use the value set in the environment variable DRD_SEGMENT_MERGING_INTERVAL if the segment merging interval has not been specified as a command-line option.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@10377 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/drd/drd_main.c b/drd/drd_main.c
index 2ca6f88..e5bc738 100644
--- a/drd/drd_main.c
+++ b/drd/drd_main.c
@@ -683,6 +683,12 @@
    DRD_(suppression_init)();
 
    DRD_(clientobj_init)();
+
+   {
+      Char* const smi = VG_(getenv)("DRD_SEGMENT_MERGING_INTERVAL");
+      if (smi)
+         DRD_(thread_set_segment_merge_interval)(VG_(strtoll10)(smi, NULL));
+   }
 }