Rename Lib to LibJna, add LibBase abstract class

bdk-kotlin/jvm/src/main/java/org/bitcoindevkit/bdk/LibBase.kt

@@ -0,0 +1,9 @@
+package org.bitcoindevkit.bdk
+
+import com.sun.jna.Native
+
+abstract class LibBase {
+    
+    protected val libJna: LibJna
+        get() = Native.load("bdk_ffi", LibJna::class.java)
+}

bdk-kotlin/jvm/src/main/java/org/bitcoindevkit/bdk/LibJna.kt

@@ -2,7 +2,7 @@ package org.bitcoindevkit.bdk
 
 import com.sun.jna.*
 
-interface Lib : Library {
+interface LibJna : Library {
 
     // typedef struct VoidResult VoidResult_t;
     class VoidResult_t : PointerType {