hid/gtk: Focus file save dialog at exit to "Save", not "Close without saving".

Avoids inadvertently loosing work when closing the application. "Cancel" would
also be a safe choice of default focus, but the choice of "Save" is copied from
gedit to help give better platform consistency on Gnome systems.
png: add explicit round() calls to the scaling

After this commit the tests pass on both 32- and 64-bit builds.
Hopefully this time it's really dead; the previous "fix" af27c2d
by myself merely increased the DPI of the output, but this one
attempts to get deterministic rounding behaviour.

Tests from folks with actual 32-bit machines are welcome.

Closes-bug: lp-860037
polygon.c: Readability cleanup for frac_circle()
Fix some broken assumptions regarding 32-bit integer coordinates in polygon1.c
Renaming SOT325 footprint to SOT353, adding SC88A footprint.

The current SOT325 footprint (as included in pcb 20100929) gives a wrong footprint w.r.t. pin orientation:

1 |  | 5
  |  | 4
2 |  | 3

this should have been:

1 |  | 5
2 |  |
3 |  | 4

Furthermore, googling for "SOT325" gives:

1) footprints in gedasymbols.org created by DJ.
2) according to www.nxp.com SOT-325-1 is a SDIP20 package (300 mil DIP).

IMO SOT325 should be renamed to SOT-353-1 --> SOT353, or SC-88A (JEITA standard) -->SC88A, or MO-203 (JEDEC standard).
The latter is not a regular name designation in pcb (yet).
All names to be converted without dashes, as not to frustrate M4.

Signed-off-by: Bert Timmerman <bert.timmerman@xs4all.nl>