<rdar://problem/11328896> Fixing a bug where regex commands were saved in the...

<rdar://problem/11328896> Fixing a bug where regex commands were saved in the history even if they came from a 'command sourced' file - this fix introduces a command sourcing depth and disables history for all levels of depth > 0, which means no commands go into history when being sourced from a file. we need an integer depth because command files might themselves source other command files, ...

llvm-svn: 157727