Kernel/LibC: Rework userspace syscall interface

Kernel syscall API no longer zeros all unused argument registers and
libc now uses inlined syscall macro internally. This significantly
cleans up generated code for basic syscall wrapper functions.

kernel/include/kernel/IDT.h

@@ -20,7 +20,7 @@ namespace Kernel
 	constexpr uint8_t IRQ_MSI_BASE      = 0x80;
 	constexpr uint8_t IRQ_MSI_END       = 0xF0;
 #if ARCH(i686)
-	constexpr uint8_t IRQ_SYSCALL       = 0xF0;
+	constexpr uint8_t IRQ_SYSCALL       = 0xF0; // hard coded in kernel/API/Syscall.h
 #endif
 	constexpr uint8_t IRQ_IPI           = 0xF1;
 	constexpr uint8_t IRQ_TIMER         = 0xF2;