Give new scopes to non-compound (simple) if-then-else substatements, correcting scoping for declarations they contain.

Also, updated several tests and the Todo list.


git-svn-id: https://cvs.khronos.org/svn/repos/ogl/trunk/ecosystem/public/sdk/tools/glslang@22845 e7fa87d3-cd2b-0410-9028-fcbf551c1848