Implement constructing vectors from matrices and matrices from scalars.
Implement constructing vectors from matrices and matrices from scalars.

BUG=15415045

Change-Id: I97355dab2890bcf3c1bf39d149960e53e4fed325
Reviewed-on: https://swiftshader-review.googlesource.com/1115
Reviewed-by: Nicolas Capens <51edc787c30f24c4904e8ffbb5523c3a9f7a451d@google.com>

bkaradzic/SwiftShader,google/swiftshader,bkaradzic/SwiftShader,bkaradzic/SwiftShader,google/swiftshader,bkaradzic/SwiftShader,google/swiftshader,bkaradzic/SwiftShader