PP: Fix issue #408: # as last character in macro.

This would look ahead for a second #, for token pasting, and if not
found, backup one token.  This is fine, unless at the end of line,
which would backup the #, rather than the look ahead.

Test/baseResults/cppBad.vert.out

@@ -0,0 +1,20 @@
+cppBad.vert
+ERROR: 0:2: 'preprocessor evaluation' : bad expression 
+ERROR: 0:2: '#if' : unexpected tokens following directive 
+ERROR: 0:3: '' : missing #endif 
+ERROR: 3 compilation errors.  No code generated.
+
+
+Shader version: 100
+ERROR: node is still EOpNull!
+0:?   Linker Objects
+
+
+Linked vertex stage:
+
+ERROR: Linking vertex stage: Missing entry point: Each stage requires one "void main()" entry point
+
+Shader version: 100
+ERROR: node is still EOpNull!
+0:?   Linker Objects
+

Test/cppBad.vert

@@ -0,0 +1,2 @@
+#define m#0#
+#if m