Front-ends: Remove now defunct afterEOF and related, use scanner's instead.

Code using atEndOfFile was dead, instead do something useful with
the scanners atEndOfInput().  This allows a better error message
for early termination of cascading errors.

hlsl/hlslParseHelper.cpp

@@ -55,7 +55,6 @@ HlslParseContext::HlslParseContext(TSymbolTable& symbolTable, TIntermediate& int
     contextPragma(true, false), loopNestingLevel(0), structNestingLevel(0), controlFlowNestingLevel(0),
     postMainReturn(false),
     limits(resources.limits),
-    afterEOF(false),
     entryPointOutput(nullptr)
 {
     // ensure we always have a linkage node, even if empty, to simplify tree topology algorithms