Interrupts: Assert if trying to install an handler on syscall vector

Installing an interrupt handler on the syscall IDT vector can lead to
fatal results, so we must assert if that happens.

Kernel/Syscall.h

@@ -32,6 +32,8 @@
 #    include <LibC/fd_set.h>
 #endif
 
+constexpr int syscall_vector = 0x82;
+
 extern "C" {
 struct timeval;
 struct timespec;