XMega PDI_ICE Memory Breakpoints

@all,
the AVRco dongle ISP3-USB and ISP3-X now support memory breakpoints
with PDI debugging of XMegas.
Because of the limited PDI debug resources in the XMegas it is not possible
to have a code breakpoint at the same time with a memory breakpoint.

This is supported:
1..2 code breakpoints, no memory breakpoint
or
1 memory breakpoint, no code breakpoint

Of course the source can contain any count of programmed breakpoints:
"Debug_Break".

A memory breakpoint for example helps to find out an unexpected access to
any byte in the IO and SRAM area. Not usable with EEprom.
Sometimes a bug in the code can destroy/overwrite memory locations and
this is very hard to find what the reason for this is. Placing a memory breakpoint
onto such a location and this location is accessed, read, write or both, the
program is immediately halted on the following opcode and the reason for
this access can be found.

Attention:
These function can only be used when the ISP3 dongle/ICE has the latest firmware!!
REV 140330_xxxx.pupd

rolf