pascal-format: Accept null precision.

pascal-format: Accept null precision.

Proof that it's valid:
------------------------- foo.pp -------------------------
program foo;
uses sysutils;
begin
  writeln(format('%.f', [3.1415926535]));
end.
----------------------------------------------------------

* gettext-tools/src/format-pascal.c: Fix comment regarding the precision.
(format_parse): Accept a null precision after '.'.
* gettext-tools/tests/format-pascal-1: Add a test case with null precision.