ext/gd: report $size with the argument number of the function called

[lacatoire]

php_imagettftext_common() backs four functions with two signatures: $size is argument 1 of imageftbbox() and imagettfbbox(), and 2 of imagefttext() and imagettftext(), which take the image first. Both size checks hardcode 2, so the bbox pair blames $angle:

imageftbbox(NAN, 0.0, $font, 'A');
// ValueError: imageftbbox(): Argument #2 ($angle) must be finite

$angle was 0.0. The type error for the same parameter already says #1, since that one comes from the arginfo:

imageftbbox('x', 0.0, $font, 'A');
// TypeError: imageftbbox(): Argument #1 ($size) must be of type float, string given

The number is now derived from the mode the helper was called in; the drawing pair keeps 2.

The added test covers all four functions, in the order the checks run: the range test precedes the finite test, so INF reports "must be between" while NAN, false against both bounds, falls through to "must be finite".

Only the two bbox messages change, so this targets master.