Remove dead leftover Makefiles from src/regress

Remove tests for executable/non-executable stack.

These tests were not portable across compilers and recently NetBSD moved
to PaX MPROTECT.

branches: 1.10.32;
Move the uvm "loan" test to tests(7).

Remove "mmap" subdir.

Require GCC for compilation

Avoid tests using nested functions when using PCC.

branches: 1.6.12;
Remove support for NetBSD/{,evb}sh5.

branches: 1.5.16; 1.5.18;
MACHINE_ARCH is x86_64 for amd64; noticed by Nicolas Joly

enable stack_noexec where a non-executable stack is supported

a simple test of uvm page loanout.

Add a check whether the stack is executable when needed, and one whether
the stack is non-executable if not explicitely enabled.
The latter one is not enabled in the Makefile yet because it cannot
succeed on platforms where the non-exec stack is not implemented.
Both checks rely on the fact that gcc puts trampoline onto the stack
for nested functions. On platforms where no such trampolines are used,
no meaningful results can be expected.
While not perfect, this is much easier than hand-coding trampolines for
each CPU type.

Add some pretty simple tests for various memory mapping facilities.
There's lots more work to do here, but this simple program found a
couple of problems which I've fixed recently.

Remove dead leftover Makefiles from src/regress

branches: 1.1.92;
Use proginstall:: to disable installing PROG.

s/defult/default/

remove unused lines.

add a makefile.

move src/sys/uvm/pdsim to src/regress/sys/uvm/pdsim.
no objection on tech-kern@.

move src/sys/uvm/pdsim to src/regress/sys/uvm/pdsim.
no objection on tech-kern@.

move src/sys/uvm/pdsim to src/regress/sys/uvm/pdsim.
no objection on tech-kern@.

add parentheses.

include string.h for memset.

move src/sys/uvm/pdsim to src/regress/sys/uvm/pdsim.
no objection on tech-kern@.

move src/sys/uvm/pdsim to src/regress/sys/uvm/pdsim.
no objection on tech-kern@.

move src/sys/uvm/pdsim to src/regress/sys/uvm/pdsim.
no objection on tech-kern@.

move src/sys/uvm/pdsim to src/regress/sys/uvm/pdsim.
no objection on tech-kern@.

#ifdef DEBUG where appropriate.

move src/sys/uvm/pdsim to src/regress/sys/uvm/pdsim.
no objection on tech-kern@.

move src/sys/uvm/pdsim to src/regress/sys/uvm/pdsim.
no objection on tech-kern@.

move src/sys/uvm/pdsim to src/regress/sys/uvm/pdsim.
no objection on tech-kern@.

move src/sys/uvm/pdsim to src/regress/sys/uvm/pdsim.
no objection on tech-kern@.