Various configure and build enhancements:
- Auto detect availability of wxWidgets, disable or enable examples build accordingly
- Enhacend (cross) toolchain detection and prefix. Now compile win32 target on linux host (--cc=i686-mingw32-gcc)

/* 
Define the i/o port global symbol 
*/

.globl _io_ports
_io_ports=0x0000	
	
/* 
0x0000 is the default mapping at reset. (it is 0x1000 for 68hc11)
*/