Bug 923: Remove dependency of CStruct annotation processor _generation_ and generated_class_user due to Java8 issues.

Java8's annotation processor as embedded within javac does not allow
referencing not-yet existing generated classes in a class source code
which will produce these generated classes via the annotation process.

Example:

+++
import com.jogamp.gluegen.structgen.CStruct;

public class Lala {
  @CStruct(name="RenderingConfig", header="TestStruct01.h")
  public RenderingConfig config;
}
+++

Above example illustrates that the type 'RenderingConfig'
does not exist at time of processing the annotation.
The type will be created via the annotation process itself.

Even though we pass '-proc:only', i.e. skip java compilation,
Java8's annotation processing via javac fails in such case.

We see this as a bug within javac's annotation processing itself!

+++

This workaround splits the annotation process and using the class as
generated by the former.

To allow this to work, CStruct receives a new field 'jname'
allowing to enforce the java-name of the structure
using a dummy field type like boolean.

  @CStruct(name="RenderingConfig", jname="RenderingConfig", header="TestStruct01.h")
  public boolean dummy;

Further more CStruct can be annotated on the package, i.e. 'package-info.java',
avoiding the dependency problem altogether.
To support multiple header files and types,
'CStructs' has been introduced using an array of 'CStruct'.

  @CStructs({@CStruct(name="RenderingConfig", header="TestStruct01.h"), @CStruct(name="Pixel", header="TestStruct02.h")})
  package com.jogamp.gluegen.test.junit.structgen;

Tests:
  - Build w/ Java7 and Java8
  - Validated 'major version 50' (Java 6) class files (OK)

1 files changed, 15 insertions, 4 deletions

diff --git a/src/java/com/jogamp/gluegen/structgen/CStruct.java b/src/java/com/jogamp/gluegen/structgen/CStruct.java
index 9d57196..be72cd8 100644
--- a/src/java/com/jogamp/gluegen/structgen/CStruct.java
+++ b/src/java/com/jogamp/gluegen/structgen/CStruct.java
@@ -33,21 +33,32 @@ import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
 /**
- *
- * @author Michael Bien
- * @author Sven Gothel, et.al.
+ * @author Michael Bien, et al.
  */
-@Target(value = {ElementType.FIELD, ElementType.LOCAL_VARIABLE})
+@Target(value = {ElementType.TYPE, ElementType.PACKAGE, ElementType.FIELD, ElementType.LOCAL_VARIABLE})
 @Retention(value = RetentionPolicy.SOURCE)
 public @interface CStruct {
 
     /**
      * Relative path to the header file.
+     * <p>
+     * Mandatory.
+     * </p>
      */
     String header();
 
     /**
      * The name of the struct.
+     * <p>
+     * Mandatory for {@link ElementType.TYPE} and {@link ElementType.PACKAGE} annotations
+     * otherwise optional.
+     * </p>
      */
     String name() default "_default_";
+
+    /**
+     * The optional java name of the struct.
+     */
+    String jname() default "_default_";
+
 }