Runtime: Fixed some broken type checks.

NB: There's a difference between the C-types "int" and "INT_TYPE"...
Stdio.Stat: Make casting work again.

lfun::cast() was declared private, which:

  * Disables it (as lfuns must be protected or public).

  * Breaks code that inherits Stdio.Stat, overloads cast(), and
    wants to call ::cast() (eg Sitebuilder.SBStat).
While having lfun::cast as private WORKS JUST FINE, it also allows us to get rid of some argument checking. As protected we can't do that.
>> now works with negative LHS again.
silence some warnings
block_allocator: fix ba_walk() and improve valgrind support

Blocks in the free list are now marked as free while the callback is
running. This helps detecting invalid accesses. Also fixed a bug in
the free list sort.
Fixed warning.
Now that we have character ranges in strings, use that for type errors from get_all_args.
This started giving deprecation errors 11 years ago.
Wrap some comments.
Remove some module_magic remnants.
Added note on environment mapping.
Pike 7.2 was released 2002. Stop supporting compat for it.
Pike 7.2 was released 2002. Stop supporting compat for it.