Adding a vector version of tooling::applyAllReplacements

One day soon, tooling::Replacements will be changed from being implemented as
an std::set to being implemented as an std::vector. Until then, some new code
using vectors of Replacements would enjoy having a version of
applyAllReplacements that takes a vector.

Differential Revision: http://llvm-reviews.chandlerc.com/D1380