term: depreciate rt, and switch to flanterm

kernel/src/sys/arch/x86_64/fpu.c

@@ -0,0 +1,14 @@
+#include <stddef.h>
+#include <stdint.h>
+
+void fpu_set_cw(const uint16_t cw) {
+	asm volatile("fldcw %0" :: "m"(cw));
+}
+
+void fpu_activate() {
+	size_t cr4;
+	asm volatile ("mov %%cr4, %0" : "=r"(cr4));
+	cr4 |= 0x200;
+	asm volatile ("mov %0, %%cr4" :: "r"(cr4));
+	fpu_set_cw(0x37F);
+}

kernel/src/sys/arch/x86_64/fpu.h

@@ -0,0 +1,6 @@
+#pragma once
+
+#include <stdint.h>
+
+void fpu_set_cw(const uint16_t cw);
+void fpu_activate();