Add ThrowableFunction.

Author: code-disaster

src/main/java/com/badlogic/gdx/function/ThrowableFunction.java

@@ -0,0 +1,14 @@
+package com.badlogic.gdx.function;
+
+/**
+ * Version of {@link java.util.function.Function} which can throw an exception.
+ *
+ * @param <T> the type of parameter passed to this consumer
+ * @param <R> the type of the function result
+ * @param <E> the type of exception to be handled
+ */
+@FunctionalInterface
+public interface ThrowableFunction<T, R, E extends Throwable> {
+
+	R apply(T t) throws E;
+}