Function to rebuild the whole grid, use it when deleting pins.

Clearer and more efficient than trying to move grid items around.
Use -p flag when making dmg temp dir.
Don't add all pins to the grid at the beginning?
Fix a null parent when creating wxStaticText.
Don't reference inexistant Clear EEPROM menu item.
Work around a wxmac 2.8 bug when appending menu items, can't have dynamic Ports menu.

In wxmac 2.8, crash when appending menu items after removing menu
items.  This seems to be fixed in 2.9.
Add missing 'string' header.
On Mac, compile for i386 for wx 2.8, and search in a couple of places for supported SDKs.
Merge remote-tracking branch 'origin/master'

Conflicts:
	firmata_mapper.cpp