- x & 3  => x % SC_BITS
- x >> 2 => x / SC_BITS
(after everything is converted to unsigned this should result in the
 exact same code as before).

This fixes opt/doms_segfault2.c.

We cannot delete the Store if its address aliases with the source of the
CopyB.

This fixes opt/loadstore3.c.

Code placement cannot handle them appropriately.

This fixes backend/sparc_keep.c.

The real issue is frontends constructing a mismatch in Call type at the
Call site and the called entity. However as these are hard to fix and
the fix here shouldn't hurt we do it in firm for now.

This fixes backend/setcc.c.