Edit HACKING & introduce cppcheck

Still a few todo according to cppcheck:

[examples/pn53x-tamashell.c:165]:
(style) Found obsolete function 'usleep'. It is recommended that new applications use the 'nanosleep' or 'setitimer' function

[libnfc/buses/uart_posix.c:343]:
(portability) Found non reentrant function 'readdir'. For threadsafe applications it is recommended to use the reentrant replacement function 'readdir_r'

[libnfc/drivers/acr122_pcsc.c:206]:
[libnfc/drivers/acr122_pcsc.c:219]:
[libnfc/drivers/acr122s.c:412]:
[libnfc/drivers/acr122s.c:425]:
[libnfc/drivers/acr122s.c:434]:
[libnfc/drivers/arygon.c:181]:
[libnfc/drivers/arygon.c:194]:
[libnfc/drivers/arygon.c:203]:
[libnfc/drivers/pn532_uart.c:158]:
[libnfc/drivers/pn532_uart.c:171]:
[libnfc/drivers/pn532_uart.c:180]:
(portability) Found non reentrant function 'strtok'. For threadsafe applications it is recommended to use the reentrant replacement function 'strtok_r'

HACKING

@@ -36,6 +36,9 @@ Here are some directions to get you started:
       $ scan-build ./configure
       $ make clean
       $ scan-build make
+      And by using cppcheck:
+      $ cppcheck --quiet --enable=all --std=c99 --std=posix \
+        -I include -I libnfc -I libnfc/buses .
     2.3 When Debianizing
       $ lintian --info --display-info --display-experimental *deb
       or (shorter version)