Include <string> for fixing undefined template on Mac.
Include <string> for fixing undefined template on Mac.

Change-Id: I4e8a860446bde7f76ea289888bf592d78c59b9c4
Reviewed-on: https://swiftshader-review.googlesource.com/21008
Reviewed-by: Nicolas Capens <51edc787c30f24c4904e8ffbb5523c3a9f7a451d@google.com>
Tested-by: Merck Hung <9ab3f9bd8652cbd7c3946b404145d0718762a769@google.com>

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