Make some implicit conversions explicit, to avoid compiler warnings.

llvm-svn: 56927
diff --git a/llvm/lib/VMCore/AsmWriter.cpp b/llvm/lib/VMCore/AsmWriter.cpp
index 6c7b68b..5d765a4 100644
--- a/llvm/lib/VMCore/AsmWriter.cpp
+++ b/llvm/lib/VMCore/AsmWriter.cpp
@@ -385,7 +385,7 @@
   
   // Find the type plane in the module map
   ValueMap::iterator MI = mMap.find(V);
-  return MI == mMap.end() ? -1 : MI->second;
+  return MI == mMap.end() ? -1 : (int)MI->second;
 }
 
 
@@ -397,7 +397,7 @@
   initialize();
   
   ValueMap::iterator FI = fMap.find(V);
-  return FI == fMap.end() ? -1 : FI->second;
+  return FI == fMap.end() ? -1 : (int)FI->second;
 }