Port [] alarm management to GRPC.

This change implements a platform independent alarm manager in alarm.c.
It's integrated with iomgr, and some tests are cleaned up.

The alarm implementation itself is a fairly direct port of LazyAlarmList from eventmanager.
SpinLock has been replaced for now with gpr_mu, and other atomic operations have been dropped (again, for now).
A majority of tests have been ported.
	Change on 2014/12/19 by ctiller <ctiller@google.com>
-------------
Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=82551363
diff --git a/build.json b/build.json
index 50f3ca3..6081a5d 100644
--- a/build.json
+++ b/build.json
@@ -1326,6 +1326,30 @@
       ]
     },
     {
+      "name": "alarm_list_test",
+      "build": "test",
+      "src": [
+        "test/core/iomgr/alarm_list_test.c"
+      ],
+      "deps": [
+        "grpc_test_util",
+        "grpc",
+        "gpr"
+      ]
+    },
+    {
+      "name": "alarm_heap_test",
+      "build": "test",
+      "src": [
+        "test/core/iomgr/alarm_heap_test.c"
+      ],
+      "deps": [
+        "grpc_test_util",
+        "grpc",
+        "gpr"
+      ]
+    },
+    {
       "name": "time_test",
       "build": "test",
       "src": [