Add support for constant folding of clamp()
Add support for constant folding of clamp()

Fixes: dEQP-GLES3.functional.shaders.constant_expressions.other.complex*
Bug: b/116598062
Change-Id: Ife2dd2edad17d6ebbd02653f484637672ce6af0a
Reviewed-on: https://swiftshader-review.googlesource.com/20828
Reviewed-by: Nicolas Capens <51edc787c30f24c4904e8ffbb5523c3a9f7a451d@google.com>
Tested-by: Chris Forbes <c3279c50043e18e9442c1ae071cafa0e7a4ca967@google.com>

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