Initial commit of Vc , version 0.7.2, copying from rootvc development branch
port changes from Matthias in vc branch:

 after fixing the Vc ROOT import script: here are the missing changes
Fix Makefile for tests
fixes for compiling with Vc types

git-svn-id: http://root.cern.ch/svn/root/branches/dev/rootvc@48448 27541ba8-7e3a-0410-8455-c3a389f83636
fixs initialization of vector for vc (use 0.0 instead of 0)

git-svn-id: http://root.cern.ch/svn/root/branches/dev/rootvc@48050 27541ba8-7e3a-0410-8455-c3a389f83636
used Vector::Scalar instead of double in utility functions for compiling with Vc types

git-svn-id: http://root.cern.ch/svn/root/branches/dev/rootvc@48449 27541ba8-7e3a-0410-8455-c3a389f83636
update to Vc 0.7 branch (soon to become 0.7.3)
update to Vc 0.7.3
Fixes for Vc compilation (use 0.0 instead of 0)
fix Vc test programs
update tests Makefile
from M. Kretz: replace two shuffle calls by Mem::permute helper to avoid bogus warning with clang
add Makefile for vc tests
remove implicit type conversion failure test
Add missing invoke_preprocessor function in configure

Fix problem using "as" on MacoS