fix memleak in GetForwardRefForGlobal()

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@57576 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AsmParser/llvmAsmParser.y b/lib/AsmParser/llvmAsmParser.y
index 54694d7..f2e6404 100644
--- a/lib/AsmParser/llvmAsmParser.y
+++ b/lib/AsmParser/llvmAsmParser.y
@@ -140,6 +140,7 @@
     GlobalValue *Ret = 0;
     if (I != GlobalRefs.end()) {
       Ret = I->second;
+      I->first.second.destroy();
       GlobalRefs.erase(I);
     }
     return Ret;