Fixed some format specifiers.

They used %hd instead of PRIdPHINT, which was not
correct anymore on a LP64 platform.
Removed some unused variables.

They are not in use anymore after the change of
function headers.
Fixed argument to notify_lowmemory_condition().

It got an enum low_memory_conditions, not
enum memory_limit_types.
Removed compiler warning.

The code for processing unary plus for the precompiler
did have a self-assignment which the compiler mentioned.
Just removed it.
Removed count().

The function was not working properly due to the
unsigned argument and was not used anyway.
Removed a compiler warning in dump_core().

Instead of provoking a crash by referencing illegal
addresses, we just restore default signal handlers for
SIGABRT (and SIGSEGV) and call abort().
It should be sufficient on modern systems to get a
coredump (if the other conditions are met).
Removed some unused functions.

get_visibility_buf() was not used anymore.
Also ins_uint32() and ins_uint16 had no users so far.
Fixed a debug_message().

The time_stamp() was missing.