Fix MSVC warning in DetectRecursion.cpp.

In preparation for turning on warnings as errors.
Review URL: https://codereview.appspot.com/5564053

git-svn-id: http://angleproject.googlecode.com/svn/trunk@959 736b8ea6-26fd-11df-bfd4-992fa37f6226
diff --git a/src/compiler/DetectRecursion.cpp b/src/compiler/DetectRecursion.cpp
index b4354fc..c09780d 100644
--- a/src/compiler/DetectRecursion.cpp
+++ b/src/compiler/DetectRecursion.cpp
@@ -60,7 +60,7 @@
 
 DetectRecursion::~DetectRecursion()
 {
-    for (int i = 0; i < functions.size(); ++i)
+    for (size_t i = 0; i < functions.size(); ++i)
         delete functions[i];
 }