Some functions in LLVMReactor.cpp and SubzeroReactor.cpp were identical
and have been moved into a common Reactor.cpp.

Bug swiftshader:21

Change-Id: Ib079757f9e35f83b1103e2791227f02775e034d3
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/27068Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>