part 2 of FORCE_ALIGNMENT fix for arduino targets.
part 2 of FORCE_ALIGNMENT fix for arduino targets.

When FORCE_ALIGNMENT was introduced for pointer aligment on 8-bit arduino targets (See idris-lang@47cd264) it was not applied to the initialization of the cheney algorithm during garbage collection. The fix modifies the start of the heap location in the same way the FORCE_ALIGNMENT-define does for the initialization of the FP-heap in alloc_heap(...) in file idris_heap.c.

To prevent duplicate code this logic has been put in the function aligned_heap_pointer(...).
markuspf/Idris-dev,markuspf/Idris-dev,kojiromike/Idris-dev,jmitchell/Idris-dev,FranklinChen/Idris-dev,kojiromike/Idris-dev,uuhan/Idris-dev,mpkh/Idris-dev,markuspf/Idris-dev,jmitchell/Idris-dev,FranklinChen/Idris-dev,uuhan/Idris-dev,markuspf/Idris-dev,mpkh/Idris-dev,mpkh/Idris-dev,FranklinChen/Idris-dev,mpkh/Idris-dev,mpkh/Idris-dev,Heather/Idris-dev,uuhan/Idris-dev,mpkh/Idris-dev,Heather/Idris-dev,jmitchell/Idris-dev,kojiromike/Idris-dev,FranklinChen/Idris-dev,kojiromike/Idris-dev,uuhan/Idris-dev,FranklinChen/Idris-dev,FranklinChen/Idris-dev,Heather/Idris-dev,jmitchell/Idris-dev,kojiromike/Idris-dev,Heather/Idris-dev,Heather/Idris-dev,markuspf/Idris-dev,markuspf/Idris-dev,kojiromike/Idris-dev,Heather/Idris-dev,uuhan/Idris-dev,markuspf/Idris-dev,uuhan/Idris-dev,uuhan/Idris-dev,jmitchell/Idris-dev,jmitchell/Idris-dev