fix broken modf family functions

src/math/i386/modf.s

 .global modf
 .type modf,@function
 modf:
-	mov 12(%esp),%eax
+	mov 12(%esp),%ecx
 	fldl 4(%esp)
-	fld1
-	fld %st(1)
-1:	fprem
-	fstsw %ax
+	fxam
+	fnstsw %ax
 	sahf
-	jp 1b
-	fstp %st(1)
-	fsubr %st(1)
-	fstpl (%eax)
+        jnp 1f
+        jc 2f
+1:      fld1
+        fld %st(1)
+1:      fprem
+        fnstsw %ax
+        sahf
+        jp 1b
+        fstp %st(1)
+        fsubr %st(0),%st(1)
+        fxch %st(1)
+        fstpl (%ecx)
+        ret
+
+2:	fstpl (%ecx)
+	mov 4(%ecx),%eax
+	and $0x80000000,%eax
+	mov %eax,4(%esp)
+	flds 4(%esp)
 	ret

src/math/i386/modff.s

 .global modff
 .type modff,@function
 modff:
-	mov 8(%esp),%eax
+	mov 8(%esp),%ecx
 	flds 4(%esp)
-	fld1
-	fld %st(1)
-1:	fprem
-	fstsw %ax
+	fxam
+	fnstsw %ax
 	sahf
-	jp 1b
-	fstp %st(1)
-	fsubr %st(1)
-	fstps (%eax)
+        jnp 1f
+        jc 2f
+1:      fld1
+        fld %st(1)
+1:      fprem
+        fnstsw %ax
+        sahf
+        jp 1b
+        fstp %st(1)
+        fsubr %st(0),%st(1)
+        fxch %st(1)
+        fstps (%ecx)
+        ret
+
+2:	fstps (%ecx)
+	mov (%ecx),%eax
+	and $0x80000000,%eax
+	mov %eax,4(%esp)
+	flds 4(%esp)
 	ret

src/math/i386/modfl.s

 .global modfl
 .type modfl,@function
 modfl:
-	mov 16(%esp),%eax
+	mov 16(%esp),%ecx
 	fldt 4(%esp)
-	fld1
-	fld %st(1)
-1:	fprem
-	fstsw %ax
+	fxam
+	fnstsw %ax
 	sahf
-	jp 1b
-	fstp %st(1)
-	fsubr %st(1)
-	fstpt (%eax)
+        jnp 1f
+        jc 2f
+1:      fld1
+        fld %st(1)
+1:      fprem
+        fnstsw %ax
+        sahf
+        jp 1b
+        fstp %st(1)
+        fsubr %st(0),%st(1)
+        fxch %st(1)
+        fstpt (%ecx)
+        ret
+
+2:	fstpt (%ecx)
+	mov 6(%ecx),%eax
+	and $0x80000000,%eax
+	mov %eax,4(%esp)
+	flds 4(%esp)
 	ret