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.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52176 91177308-0d34-0410-b5e6-96231b3b80d8

test/FrontendC/libcalls.c

@@ -4,6 +4,8 @@
 // RUN: %llvmgcc %s -S -emit-llvm -O1 -o - | grep {call.*ldexp}
 // RUN: %llvmgcc %s -S -emit-llvm -O3 -fno-builtin -o - | grep {call.*exp2f}
 
+float exp2f(float);
+
 float t4(unsigned char x) {
   return exp2f(x);
 }