A-10C: add CDU export

Special characters are encoded as follows:

Symbol, description, character code

BRANCH_L, arrow to the right, 0xBB
BRANCH_R, arrow to the left, 0xAB
ROTARY, up/down arrow, 0xAE
DATA_ENTRY, "[]", 0xA1
SYS_ACTION, "bullseye", 0xA9
DEGREE, °, 0xB0
FILLED, CDU cursor, 0xB6
INC_DEC, +/- symbol, 0xB1