math: add (obsolete) bsd drem and finite functions
diff --git a/src/math/finitef.c b/src/math/finitef.c
new file mode 100644
index 0000000..2c4c771
--- /dev/null
+++ b/src/math/finitef.c
@@ -0,0 +1,7 @@
+#define _GNU_SOURCE
+#include <math.h>
+
+int finitef(float x)
+{
+	return isfinite(x);
+}