ENH: consistency improvements for keyType and wordRe

- simplify compile/uncompile, reading, assignment

- implicit construct wordRe from keyType (was explicit) to simplify
  future API changes.

- make Foam::isspace consistent with std::isspace (C-locale)
  by including vertical tab and form feed

ENH: improve #ifeq float/label comparisons

tutorials/IO/dictionary/good-if3.dict

@@ -0,0 +1,31 @@
+/*--------------------------------*- C++ -*----------------------------------*\
+| =========                 |                                                 |
+| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
+|  \\    /   O peration     | Version:  v2012                                 |
+|   \\  /    A nd           | Website:  www.openfoam.com                      |
+|    \\/     M anipulation  |                                                 |
+\*---------------------------------------------------------------------------*/
+FoamFile
+{
+    version     2.0;
+    format      ascii;
+    class       dictionary;
+    object      dictionary;
+}
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+// (label == scalar) ?
+#ifeq 0 0.0
+labelEqScalar true;
+#else
+labelEqScalar false; } // Provoke parse error if we see this branch
+#endif
+
+// (scalar == label) ?
+#ifeq 0.0 0
+scalarEqLabel true;
+#else
+scalarEqLabel false; } // Provoke parse error if we see this branch
+#endif
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //