Add Gradle build

Fixed warnings about missing deprecation annotation and variable name in
one test failing on Java greater version 9.

This commit is simpler then
5847ee4d97

build.gradle

@@ -0,0 +1,46 @@
+/*
+ * This file was generated by the Gradle 'init' task.
+ *
+ * This generated file contains a sample Java Library project to get you started.
+ * For more details take a look at the Java Libraries chapter in the Gradle
+ * User Manual available at https://docs.gradle.org/6.6.1/userguide/java_library_plugin.html
+ */
+
+plugins {
+    // Apply the java-library plugin to add support for Java Library
+    id 'java-library'
+}
+
+version = '3.0.2'
+group = 'org.luaj'
+
+sourceCompatibility = 1.8
+
+sourceSets {
+    main {
+        java {
+            srcDirs=['src/core', 'src/jme', 'src/jse']
+        }
+    }
+    test {
+        java {
+            srcDirs=['test/java', 'test/junit']
+        }
+    }
+}
+
+repositories {
+    // Use jcenter for resolving dependencies.
+    // You can declare any Maven/Ivy/file repository here.
+    jcenter()
+}
+
+dependencies {
+    // Apache Commons Bytecode Engineering Library
+    implementation 'org.apache.bcel:bcel:6.5.0'
+    // MicroEmu is a pure Java implementation of Java ME
+    implementation 'org.microemu:microemulator:2.0.4'
+
+    // Use JUnit test framework
+    testImplementation 'junit:junit:4.13'
+}