Fix printing of terminal commas in designated initializers.
Fix printing of terminal commas in designated initializers.

Also fix some style-related FIXMEs that don't affect behaviour.

mstorsjo/c99-to-c89,rbultje/c99-to-c89,rbultje/c99-to-c89,libav/c99-to-c89,libav/c99-to-c89,mstorsjo/c99-to-c89