HLSL: Correct use of isPerVertexBuiltIn() to be isClipOrCullDistance().

This allows removal of isPerVertexBuiltIn(). It also leads to
removal of addInterstageIoToLinkage(), which is no longer needed.

Includes related name improvements.

Test/baseResults/hlsl.scalarCast.vert.out

@@ -158,6 +158,7 @@ Shader version: 500
 0:29            Constant:
 0:29              1 (const int)
 0:?   Linker Objects
+0:?     '@entryPointOutput_position' ( out 4-component vector of float Position)
 0:?     '@entryPointOutput' (layout( location=0) out structure{ temp 2-component vector of float texCoord})
 
 
@@ -323,6 +324,7 @@ Shader version: 500
 0:29            Constant:
 0:29              1 (const int)
 0:?   Linker Objects
+0:?     '@entryPointOutput_position' ( out 4-component vector of float Position)
 0:?     '@entryPointOutput' (layout( location=0) out structure{ temp 2-component vector of float texCoord})
 
 // Module Version 10000