Move to root 5.34.22.
Drop unneeded llvm patches.
New xrootd 4.0.4

- Move to new version.
- Cleanup obsolete patches.
Move to new boost 1.57.00
Merge pull request #1212 from ktf/update-7-4-x

Updating key externals for CMSSW_7_4_X
Merge remote branch 'origin/IB/CMSSW_7_4_X/stable' into IB/CMSSW_7_0_X/stable