Use correct native library on OpenJDK on AIX

It seems System#mapLibraryName from OpenJDK works differently on AIX
than OpenJ9. OpenJ9 expands jnidispatch to libjnidispatch.a, while
OpenJDK expands it to libjnidispatch.so. This in turn causes the
loader to search for the wrong file.

java-native-access#1066

src/com/sun/jna/Native.java

@@ -999,7 +999,13 @@ private static void loadNativeDispatchLibrary() {
      */
     private static void loadNativeDispatchLibraryFromClasspath() {
         try {
-            String libName = "/com/sun/jna/" + Platform.RESOURCE_PREFIX + "/" + System.mapLibraryName("jnidispatch").replace(".dylib", ".jnilib");
+            String mappedName = System.mapLibraryName("jnidispatch").replace(".dylib", ".jnilib");
+            if(Platform.isAIX()) {
+                // OpenJDK is reported to map to .so -- this works around the
+                // difference between OpenJ9 and OpenJDK
+                mappedName = "libjnidispatch.a";
+            }
+            String libName = "/com/sun/jna/" + Platform.RESOURCE_PREFIX + "/" + mappedName;
             File lib = extractFromResourcePath(libName, Native.class.getClassLoader());
             if (lib == null) {
                 if (lib == null) {