A couple of fixes regarding handles drawing and selection due to changes in my previous patches:
- Now text alignment is correct for effect strips that have inputs (and so no handles drawn)
- select_box(handles) now skips those strips, and also locked ones
- select() now avoid selecting locked strips' handles
- Small clean-up in sequencer_draw.c
- sequence_handle_size_get_clamped() --> sequence_handle_pixelsize_get()
- handsize_clamped --> handsize
- Pass handsize as an argument of calculate_seq_text_offsets() instead of calculating it again
