math: fix aliasing violation in long double wrappers

modfl and sincosl were passing long double* instead of double*
to the wrapped double precision functions (on archs where long
double and double have the same size).
This is fixed now by using temporaries (this is not optimized
to a single branch so the generated code is a bit bigger).
Found by Morten Welinder.

src/math/modfl.c

@@ -3,7 +3,12 @@
 #if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
 long double modfl(long double x, long double *iptr)
 {
-	return modf(x, (double *)iptr);
+	double d;
+	long double r;
+
+	r = modf(x, &d);
+	*iptr = d;
+	return r;
 }
 #elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
 #if LDBL_MANT_DIG == 64

src/math/sincosl.c

@@ -4,7 +4,10 @@
 #if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
 void sincosl(long double x, long double *sin, long double *cos)
 {
-	sincos(x, (double *)sin, (double *)cos);
+	double sind, cosd;
+	sincos(x, &sind, &cosd);
+	*sin = sind;
+	*cos = cosd;
 }
 #elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
 void sincosl(long double x, long double *sin, long double *cos)