added portPOINTER_SIZE_TYPE and SIZE_MAX definition to PIC24/dsPIC port (#636)

* added portPOINTER_SIZE_TYPE definition to PIC24/dsPIC port

* Added SIZE_MAX definition to PIC24/dsPIC33

Author: n9wxu

portable/MPLAB/PIC24_dsPIC/portmacro.h

@@ -51,6 +51,8 @@ extern "C" {
 #define portSHORT       short
 #define portSTACK_TYPE  uint16_t
 #define portBASE_TYPE   short
+#define portPOINTER_SIZE_TYPE size_t
+#define SIZE_MAX    ( ( size_t ) -1 )
 
 typedef portSTACK_TYPE StackType_t;
 typedef short BaseType_t;