Fix some llvm-gcc warnings in testcases, mostly by adding includes or adding
declarations. These are the fixes that I was pretty confident about, there are
still a lot of other llvm-gcc warnings of which I'm not sure if they can be
safely ignored or fixed, without breaking the test case.

This fixes 11 testcases.

llvm-svn: 52176
diff --git a/llvm/test/FrontendC++/2005-02-11-AnonymousUnion.cpp b/llvm/test/FrontendC++/2005-02-11-AnonymousUnion.cpp
index b0ff7e7..87ababc 100644
--- a/llvm/test/FrontendC++/2005-02-11-AnonymousUnion.cpp
+++ b/llvm/test/FrontendC++/2005-02-11-AnonymousUnion.cpp
@@ -21,7 +21,7 @@
 }
 
 // Make sure that normal unions work.  duh :)
-volatile union {
+volatile union U_t {
   short S;
   int i;
 } U;