Correct off-by-whatever errors of the source position in parse_select_expression().
[cparser] / lextest /
drwxr-xr-x   ..
-rwxr-xr-x 246 do_tests.sh
drwxr-xr-x - legalc
drwxr-xr-x - preprocessor
drwxr-xr-x - tokenstreams
drwxr-xr-x - warnings