* src/pic16/gen.c (genrshTwo): fixed sign extension

* src/pic16/gen.c (genrshTwo): fixed sign extension
* src/pic16/device.c: added pic18f2320, 4220 and 4320
* device/include/pic16/pic18f2220.h: changed some bit definitions,
  added T0CONbits
* device/include/pic16/pic18f4220.h: NEW, header for
  pic18f4220 and pic18f4320
* device/include/pic16/pic18fregs.h: added new devices,
  embraced Nop(), ClrWdt(), Sleep() and Reset() with do {} while(0)
* device/include/pic16/signal.h: resolved name clashes
  on bit definitions, added DEF_HANDLER2(sig1,sig2,handler)
  to also allow testing for interrupt enable bits, added
  comments on how to use the macros
* device/lib/pic16/libdev/pic18f2220.c: added T0CONbits
* device/lib/pic16/libdev/pic18f{2320,4220,4320}.c: NEW,
  register definitions for the devices
* device/lib/pic16/pics.all: added new devices
* device/lib/pic16/libc/stdlib/calloc.c: fixed zeroing
  allocated memory
* device/lib/pic16/libc/stdlib/memfree: do not count
  the block header as free memory
* device/lib/pic16/libc/stdlib/memmisc.c (_initHeap):
  simplified and added missing end-of-blocklist-marker
  (reported by Peter Onion, fixes #1252814)
* (_mergeHeapBlock): fixed loop condition
* device/lib/pic16/libc/stdlib/realloc.c: return NULL for
  len==0, restructured code
* device/lib/pic16/libc/stdlib/{malloc,memfreemax}.c: cleaned
  up a bit, reduced bitfield accesses, prevent endless loops
  in case of heap corruption
* device/lib/pic16/libc/stdlib/x_ftoa.c: disabled
  "unreferenced arguments/must return a value" warnings
* device/lib/pic16/libio/usart/ubaud.c (usart_baud):
  replaced BAUDREG with SPBRG
* device/lib/pic16/libsdcc/lregs/{lrrest.c,lrst.c},
  device/lib/pic16/debug/gstack/gstack.c: replaced
  _naked, _asm, _endasm with __naked, __asm, __endasm

git-svn-id: https://sdcc.svn.sourceforge.net/svnroot/sdcc/trunk/sdcc@3835 4a8a32a2-be11-0410-ad9d-d568d2c75423