Fix portability issues in
86c43f4e22c0771fd0cc6bce2799802c894ee2ec.
INT64_MIN/MAX should be spelled PG_INT64_MIN/MAX, per well established
convention in our sources. Less obviously, a symbol named DOUBLE causes
problems on Windows builds, so rename that to DOUBLE_CONST; and rename
INTEGER to INTEGER_CONST for consistency.
Also, get rid of incorrect/obsolete hand-munging of yycolumn, and fix
the grammar for float constants to handle expected cases such as ".1".
First two items by Michael Paquier, second two by me.