Revert "Move XBuf to optional libs"

This reverts commit 84363b70f85512af9a7007d137cf1b021091dbf1.

build.gradle

@@ -43,6 +43,9 @@ configurations {
 }
 
 dependencies {
+
+    corelibs dep("com.github.xbuf:jme3_xbuf:0.9.1", false, false)
+
     corelibs dep("org.jmonkeyengine:jme3-core:$jmeEngineVersion", true, true)
     corelibs dep("org.jmonkeyengine:jme3-desktop:$jmeEngineVersion", true, true)
     corelibs dep("org.jmonkeyengine:jme3-lwjgl:$jmeEngineVersion", true, true)
@@ -65,8 +68,6 @@ dependencies {
     optlibs dep("org.jmonkeyengine:jme3-ios:$jmeEngineVersion", true, true)
     optlibs dep("org.jmonkeyengine:jme3-android-native:$jmeEngineVersion", true, true)
     optlibs dep("org.jmonkeyengine:jme3-bullet-native-android:$jmeEngineVersion", true, true)
-    optlibs dep("com.github.xbuf:jme3_xbuf:0.9.1", false, false)
-    
     testdatalibs dep("org.jmonkeyengine:jme3-testdata:$jmeEngineVersion", false, false)
 
     examplelibs dep("org.jmonkeyengine:jme3-examples:$jmeEngineVersion", false, true)