add math/rand (#403)

c/math/rand

c/math/rand/rand.go

@@ -0,0 +1,23 @@
+package rand
+
+import (
+	_ "unsafe"
+
+	"github.com/goplus/llgo/c"
+)
+
+const (
+	LLGoPackage = "decl"
+)
+
+//go:linkname Rand C.rand
+func Rand() c.Int
+
+//go:linkname RandR C.rand_r
+func RandR(*c.Uint) c.Int
+
+//go:linkname Srand C.srand
+func Srand(c.Uint)
+
+//go:linkname Sranddev C.sranddev
+func Sranddev()