Add header guards to some headers that are missing them

Also adjust some of dsymutil's headers to put the header guards at the top,
otherwise the compiler will not recognize them as header guards.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@341323 91177308-0d34-0410-b5e6-96231b3b80d8
10 files changed