New, more flexible, parser context datatype that includes and extends

the previous flags allowForest and allowVarRef.
Added binary operator (work in progress).
Better implementation of +=,-=,*=, and /= (new) operators.

t_fractions_test.go

@@ -34,7 +34,8 @@ func TestFractionsParser(t *testing.T) {
 		/*  21 */ {`fract(1,0)`, nil, `fract(): division by zero`},
 		/*  22 */ {`string(1|2)`, "1|2", nil},
 	}
-	runTestSuite(t, section, inputs)
+	runTestSuiteSpec(t, section, inputs, 1)
+	// runTestSuite(t, section, inputs)
 }
 
 func TestFractionToStringSimple(t *testing.T) {