configure: fix tests for 2-arg math functions

Signed-off-by: Mans Rullgard <mans@mansr.com>

configure

@@ -785,11 +785,13 @@ EOF
 check_mathfunc(){
     log check_mathfunc "$@"
     func=$1
-    shift
+    narg=$2
+    shift 2
+    test $narg = 2 && args="f, g" || args="f"
     disable $func
     check_ld "$@" <<EOF && enable $func
 #include <math.h>
-float foo(float f) { return $func(f); }
+float foo(float f, float g) { return $func($args); }
 int main(void){ return 0; }
 EOF
 }
@@ -3306,8 +3308,12 @@ done
 check_lib math.h sin -lm && LIBM="-lm"
 enabled vaapi && require vaapi va/va.h vaInitialize -lva
 
+atan2f_args=2
+ldexpf_args=2
+powf_args=2
+
 for func in $MATH_FUNCS; do
-    check_mathfunc $func
+    eval check_mathfunc $func \${${func}_args:-1}
 done
 
 # these are off by default, so fail if requested and not available