Simplify architecture and C++11 flags checking and usage.
Simplify architecture and C++11 flags checking and usage.

Based on patch from Khouri Giordano. Thanks!

Conflicts:
	tests/CMakeLists.txt

VcDevel/Vc,VcDevel/Vc,VcDevel/Vc,chr-engwer/Vc,VcDevel/Vc,chr-engwer/Vc,chr-engwer/Vc