Break Foundation import cycles for strict graph sorting

Disentangle circular dependencies Foundation framework primitives using
forward declarations.

Foundation/CPException.j

@@ -20,11 +20,10 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
-@import "CPCoder.j"
 @import "CPObject.j"
 @import "CPString.j"
 
-@class CPString
+@class CPCoder
 
 CPInvalidArgumentException          = @"CPInvalidArgumentException";
 CPUnsupportedMethodException        = @"CPUnsupportedMethodException";

Foundation/CPString.j

@@ -20,17 +20,15 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
-@import "CPException.j"
 @import "CPObject.j"
 @import "CPObjJRuntime.j"
 @import "CPRange.j"
-@import "CPSortDescriptor.j"
-@import "CPURL.j"
 @import "CPValue.j"
 @import "CPNull.j"
 
 @class CPException
 @class CPURL
+@class CPSortDescriptor
 
 @global CPInvalidArgumentException
 @global CPRangeException

Foundation/CPValue.j

@@ -20,9 +20,10 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
-@import "CPCoder.j"
 @import "CPObject.j"
 
+@class CPCoder
+
 /*!
     @class CPValue
     @ingroup foundation