Fix interrupt trap gates

Until now the code would set the most significant bit in the type part
of the IDT descriptor for trap gates as a result of my error, causing a
triple fault when trying to handle a double fault. A less significant, but still
noteworthy change is that the double fault handler has been slightly revamped to
print out :( on a red background and no longer spits out a warning because I
accidentally wrote a string there, not a char.