Fix inverted condition resulting in spurious warnings
Partly fix GTK2 image generation
Change the GTK2.Toolbar example images to use non-deprecated (and actually implemented) APIs
Some tweaks to Stdio.IOBuffer:

o The various functions that add data now return the buffer
o It is now possible to overload the range_error method.
  This can be used to fill the buffer on demand.
Added support for SO_REUSEPORT when available
Call rint instead of RINT.
It hasn't been possible to compile Pike without strncmp since 2003. Remove port code for it.
Added add_ints() method to IOBuffer.
Exploit the newest features of IOBuffer
IOBuffer: Use apply_current() to call range_error().

This gets rid of a dynamic lookup and a reference on the
string "range_error".

It also improves the odds that IOBuffer will support being
inherited multiple times, as well as private inherit.
Build: Support other make(1) than GNU-make.

This also helps when building source dists.
Silence warnings.
Removed some unused tests.