GlueGen: Add support for 'compound call-by-value', i.e. passing and returning struct instance

'compound call-by-value' is not efficient.

However, to allow mapping APIs utilizing passing small structs
as arguments and return values - this feature has been added.

+++

To return the struct value, native code needs to
allocate a NIO ByteBuffer and copy the data.
The stack return value can be dismissed afterwards and the
NIO buffer is returned.

We include this functionality for all generated [impl] classes,
native method:
  'static jobject JVMUtil_NewDirectByteBufferCopy(JNIEnv *env, void * source_address, jlong capacity)'

  (See: 'JavaEmitter.initClassAccessCode')

Since this code requires knowledge of java classes and methods,
for which a reference needs to be acquired, a static initialization method
has been introduced for all generated [impl] classes:
  'private static native boolean initializeImpl();'

Per default the this method will be called in the new
static initializer block of the class,
which can be supressed via the configuration element:
   'ManualStaticInit <class-name>'

'ManualStaticInit' can be used to issue the 'initializeImpl()'
call in a custom static initializer written by the user.

However, at the time 'initializeImpl()' gets called
the JNI native library must have been loaded, of course!

+++

- See tag: // FIXME: Compound call-by-value
  for code changes and validation of completeness

Trigger for compond call-by-value in CMethodBindingEmitter is:
   !cArgType.isPointer() && javaArgType.isCompoundTypeWrapper()

Trigger for compond call-by-value in JavaEmitter is:
  t.isCompound()

+++

Further more we do tolerate 'javaType.isCPrimitivePointerType()',
i.e. adding comments for offset/size and field entries,
which are all NOP.

This allows to utilize the remaining fields of the native structure.

+++

Tests: Added call-by-value to test1.[ch] binding test!

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