* src/pic/gen.c (popGetExternal): augmented to also create references

* src/pic/gen.c (popGetExternal): augmented to also create references
  to external variables (not only labels),
  (genCall): comment on plan to reduce PAGESEL overhead,
  (genFunction, genEndFunction): also save/restore FSR around interrupt
  handling code, removed lots of unused code
  (genDivOneByte): release acquired temp register
* src/pic/glue.c (pic14createInterruptVect): adadt to new signature
  of popGetExternal
* device/lib/pic/libsdcc/shadowregs.c: NEW, provide storage location
  for registers that need to be saved during interrupts (FSR, STATUS,
  PCLATH; W needs special handling), currently only FSR is used

git-svn-id: https://sdcc.svn.sourceforge.net/svnroot/sdcc/trunk/sdcc@4708 4a8a32a2-be11-0410-ad9d-d568d2c75423