Revert "[Implicit Modules] Add -cc1 option -fmodules-strict-context-hash which...

Revert "[Implicit Modules] Add -cc1 option -fmodules-strict-context-hash which includes search paths and diagnostics." and "[Docs] Fix header level."

The test doesn't work on Windows. I'll fix it and recommit later.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@375338 91177308-0d34-0410-b5e6-96231b3b80d8