Fixup for #6 (native signature format detection) (#8)

* Fixup for #6

Behaviour was changed in the JNI wapper but not in Kotlin native code.

* Set version to 0.2.1-1.4-M3

tests/src/commonTest/kotlin/fr/acinq/secp256k1/Secp256k1Test.kt

@@ -1,5 +1,6 @@
 package fr.acinq.secp256k1
 
+import kotlin.random.Random
 import kotlin.test.*
 
 
@@ -265,4 +266,24 @@ class Secp256k1Test {
             Hex.encode(der).toUpperCase(),
         )
     }
+
+    @Test
+    fun testFormatConversion() {
+        val random = Random.Default
+
+        fun randomBytes(length: Int): ByteArray {
+            val buffer = ByteArray(length)
+            random.nextBytes(buffer)
+            return buffer
+        }
+
+        repeat(200) {
+            val priv = randomBytes(32)
+            val pub = Secp256k1.pubkeyCreate(priv)
+            val data = randomBytes(32)
+            val sig = Secp256k1.sign(data, priv)
+            val der = Secp256k1.compact2der(sig)
+            Secp256k1.verify(der, data, pub)
+        }
+    }
 }