Add constant folding for the exp*(), log*(), *sqrt(), round*(), floor(),...

Add constant folding for the exp*(), log*(), *sqrt(), round*(), floor(), fract(), ceil(), abs(), and sign() built in functions.


git-svn-id: https://cvs.khronos.org/svn/repos/ogl/trunk/ecosystem/public/sdk/tools/glslang@21927 e7fa87d3-cd2b-0410-9028-fcbf551c1848