Fix signedness in cmap interface.
Use code space ranges when remapping ToUnicode CMaps.
Fix 695101 and 694114: Use the correct numbers to validate the encryption key length.

This reverts commit b1ed116091b790223a976eca2381da2875341e10.

The key length for V==2 must be 40 <= length <= 128.
The key length for V==4 is not taken from the /Length entry.