Support "z" input constraint

[4ntoine]

/Applications/A.app/Contents/Resources/Java/hardware/a/cores/a/wiring_analog.c:120:10: error: 
      invalid input constraint 'z' in asm
                switch(digitalPinToTimer(pin))
                       ^
/Applications/A.app/Contents/Resources/Java/hardware/a/cores/a/A.h:143:32: note: expanded
      from macro 'digitalPinToTimer'
#define digitalPinToTimer(P) ( pgm_read_byte( digital_pin_to_timer_PGM + (P) ) )
                               ^
/Applications/A.app/Contents/Resources/Java/hardware/tools/avr/avr/include/avr/pgmspace.h:696:41: note: 
      expanded from macro 'pgm_read_byte'
#define pgm_read_byte(address_short)    pgm_read_byte_near(address_short)
                                        ^
/Applications/A.app/Contents/Resources/Java/hardware/tools/avr/avr/include/avr/pgmspace.h:410:43: note: 
      expanded from macro 'pgm_read_byte_near'
#define pgm_read_byte_near(address_short) __LPM((uint16_t)(address_short))
                                          ^
/Applications/A.app/Contents/Resources/Java/hardware/tools/avr/avr/include/avr/pgmspace.h:398:29: note: 
      expanded from macro '__LPM'
#define __LPM(addr)         __LPM_classic__(addr)
                            ^
/Applications/A.app/Contents/Resources/Java/hardware/tools/avr/avr/include/avr/pgmspace.h:261:11: note: 
      expanded from macro '__LPM_classic__'
        : "z" (__addr16)        \
          ^

[4ntoine]

code:

#define __LPM_classic__(addr)   \
(__extension__({                \
    uint16_t __addr16 = (uint16_t)(addr); \
    uint8_t __result;           \
    __asm__                     \
    (                           \
        "lpm" "\n\t"            \
        "mov %0, r0" "\n\t"     \
        : "=r" (__result)       \
        : "z" (__addr16)        \
        : "r0"                  \
    );                          \
    __result;                   \
}))

[dylanmckay]

Closing because the issue is a symptom of issue #23