[psteinroe]

With plpgsql_check installed, editing a PL/pgSQL function no longer underlines the entire function body.

Located compile errors

Errors that stop the function from compiling, like a misspelled DECLARE, a missing END IF or an unknown variable, come from plpgsql_check without a statement. They only have the body and a character position, so we fell back to the whole body. They now point at the token at that position, or at the delimiter in syntax error at or near ";". Errors at end of input still span the body.

Whole-body libpg_query error

libpg_query's PL/pgSQL syntax error has no usable location: cursorpos is always 0, and its "near line N" is the last parsed statement, not the error. It is now dropped for every function that plpgsql_check actually checked. It is still reported when plpgsql_check can't check the function: no database, extension missing or disabled, the function fails to create, or no trigger uses a trigger function.

#860 (draft) also touches database_diagnostics; whichever merges second needs a small rebase.

Refs #179