defer statement logging until after parse

The attached patch is for review, not application. It defers logging
statements until after they have been parsed. There should be no
observable difference in behaviour if there is a successful parse, and
on error the following traces appear:

line:3 ERROR: syntax error at or near "se3d2" at character 1
line:4 LOG: parse error in statement: se3d2 aaa;

Basically, I want to know that this will not break anything, and if so I
will use it as the basis for a selective statement logging facility,
based on the command tag(s) of the parsed statement(s), and
incorporating Greg Stark's suggesion of a "syntax error" logging level.

cheers

andrew