Kernel/userspace: rework floating point math

SSE is now unconditionally enabled any where and most of math.h is now
actually implemented. using __builtin_<func> lead to many hangs where
the builtin function would just call itself.

userspace/libraries/LibC/include/fenv.h

@@ -7,7 +7,46 @@
 
 __BEGIN_DECLS
 
-// FIXME
+#include <stdint.h>
+
+#define FE_INVALID   (1 << 0)
+#define FE_DIVBYZERO (1 << 2)
+#define FE_OVERFLOW  (1 << 3)
+#define FE_UNDERFLOW (1 << 4)
+#define FE_INEXACT   (1 << 5)
+#define FE_ALL_EXCEPT (FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW | FE_INEXACT)
+
+#define FE_TONEAREST  0
+#define FE_DOWNWARD   1
+#define FE_UPWARD     2
+#define FE_TOWARDZERO 3
+
+typedef struct {
+	uint32_t control;
+	uint32_t status;
+	uint32_t __unused[5];
+} __x87_fpu_t;
+
+typedef struct {
+	__x87_fpu_t x87_fpu;
+	uint32_t mxcsr;
+} fenv_t;
+
+typedef uint8_t fexcept_t;
+
+#define FE_DFL_ENV ((const fenv_t*)0x1)
+
+int feclearexcept(int);
+int fegetenv(fenv_t*);
+int fegetexceptflag(fexcept_t*, int);
+int fegetround(void);
+int feholdexcept(fenv_t*);
+int feraiseexcept(int);
+int fesetenv(const fenv_t*);
+int fesetexceptflag(const fexcept_t*, int);
+int fesetround(int);
+int fetestexcept(int);
+int feupdateenv(const fenv_t*);
 
 __END_DECLS