Clean up the mess from => patch.

Commit 865f14a2d3 was quite a few bricks
shy of a load: psql, ecpg, and plpgsql were all left out-of-step with
the core lexer.  Of these only the last was likely to be a fatal
problem; but still, a minimal amount of grepping, or even just reading
the comments adjacent to the places that were changed, would have found
the other places that needed to be changed.

src/include/parser/scanner.h

@@ -50,7 +50,7 @@ typedef union core_YYSTYPE
  * the ASCII characters plus these:
  *	%token <str>	IDENT FCONST SCONST BCONST XCONST Op
  *	%token <ival>	ICONST PARAM
- *	%token			TYPECAST DOT_DOT COLON_EQUALS
+ *	%token			TYPECAST DOT_DOT COLON_EQUALS EQUALS_GREATER
  * The above token definitions *must* be the first ones declared in any
  * bison parser built atop this scanner, so that they will have consistent
  * numbers assigned to them (specifically, IDENT = 258 and so on).