* src/SDCCsymt.c (compStructSize): allow signed bitfields for PIC ports

* src/SDCCsymt.c (compStructSize): allow signed bitfields for PIC ports
* src/pic16/gen.c (genUnpackBits): support signed bitfields,
  (genAssign): emit warning when casting literals to generic pointer
    type, also applies when taking the address of a fixed variable,
  (genCast): improved casting to generic pointers
* src/pic16/glue.c (pic16emitStaticSeg): fixed(?) handling of fixed
  extern variables, added verbose error message
* device/include/pic16/{string.h,errno.h}: added #pragma library c

git-svn-id: https://sdcc.svn.sourceforge.net/svnroot/sdcc/trunk/sdcc@3912 4a8a32a2-be11-0410-ad9d-d568d2c75423