[LCG] Hoist the definitions of the stream operator friends to be inline

[LCG] Hoist the definitions of the stream operator friends to be inline
friend definitions.

Based on the experiments Sean Silva and Reid did, this seems the safest
course of action and also will work around a questionable warning
provided by GCC6 on the old form of the code. Thanks for Davide pointing
out the issue and other suggesting ways to fix.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@274740 91177308-0d34-0410-b5e6-96231b3b80d8