Kernel: fix signal handler block mask restoration

kernel/arch/i686/Signal.S

@@ -59,7 +59,7 @@ signal_trampoline:
 	addl $24, %esp
 
 	// restore sigmask
-	movl $83, %eax      // SYS_SIGPROCMASK
+	movl $79, %eax      // SYS_SIGPROCMASK
 	movl $3,  %ebx      // SIG_SETMASK
 	leal 72(%esp), %ecx // set
 	xorl %edx, %edx     // oset

kernel/arch/x86_64/Signal.S

@@ -61,7 +61,7 @@ signal_trampoline:
 	addq $40, %rsp
 
 	// restore sigmask
-	movq $83, %rdi       // SYS_SIGPROCMASK
+	movq $79, %rdi       // SYS_SIGPROCMASK
 	movq $3,  %rsi       // SIG_SETMASK
 	leaq 192(%rsp), %rdx // set
 	xorq %r10, %r10      // oset

kernel/kernel/Thread.cpp

@@ -10,10 +10,14 @@
 #include <kernel/Thread.h>
 #include <kernel/Timer/Timer.h>
 #include <kernel/UserCopy.h>
+#include <sys/syscall.h>
 
 namespace Kernel
 {
 
+	static_assert(SYS_SIGPROCMASK == 79, "this is hard coded in arch/*/Signal.S");
+	static_assert(SIG_SETMASK     ==  3, "this is hard coded in arch/*/Signal.S");
+
 #if ARCH(x86_64)
 	static constexpr vaddr_t s_user_stack_addr_start = 0x0000700000000000;
 #elif ARCH(i686)