* i8086 small and tiny memory model ppus made incompatible. Rationale:
  o the maintenance effort will be less - previously we had to test 4
    combinations:
      tiny program with tiny rtl
      tiny program with small rtl
      small program with tiny rtl
      small program with small rtl
    I only tested both tiny and small programs with the small rtl, so I missed
    a bug, which caused small programs built with the tiny rtl to always give
    a "Nil pointer assignment" error. Now we only need to test two cases:
      tiny program with tiny rtl
      small program with small rtl
  o I'm planning a bug fix for interrupt procedures in the tiny model, which
    will make their prolog differ between small and tiny. Currently, they're
    not used in the rtl, but that may change. And even if it doesn't,
    interrupt procedures may also be used by user units.

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@27516 3ad0048d-3df7-0310-abae-a5850022a9f2