This adds an option to use a heap-buffer for the usually stack-based
`MP_WARRAY`-sized temporary buffers.

Per default it will reserve a single buffer, which can be modified
* at compile-time via the `MP_WARRAY_NUM` define
* at run-time by calling `mp_warray_init()`

The internal structure can only be created once. If one wants to modify
the maximum number of elements, the entire structure has to be free'd
by calling `mp_warray_free()`.

In case one wants to use this option with multiple threads, one shall
use the `mp_warray_init()` function and pass appropriate locking functions.

Signed-off-by: Steffen Jaeckel <s@jaeckel.eu>

`s_warray_init()` and `s_warray_free()` are not safe and MUST NOT be called
from multiple threads.

This also removes `MP_WARRAY_NUM`, since automatic initialization will not
be safe for more than one thread.

Signed-off-by: Steffen Jaeckel <s@jaeckel.eu>

To be able to support this for MSVC as well, we have to move this into a
separate private API function.

Signed-off-by: Steffen Jaeckel <s@jaeckel.eu>

Output gets garbeled a bit, but we only care for the result which is
`Tests OK/NOP/FAIL: 50/0/0`.

Add `-Wno-incomplete-setjmp-declaration` since `clang-10` shipping with
Ubuntu 20.04 seems broken... and `-Wno-unknown-warning-option` since
`clang-8` doesn't know about this warning...

Signed-off-by: Steffen Jaeckel <s@jaeckel.eu>

... and fix some MSVC related (and other) things.

Signed-off-by: Steffen Jaeckel <s@jaeckel.eu>

Signed-off-by: Steffen Jaeckel <s@jaeckel.eu>

Signed-off-by: Steffen Jaeckel <s@jaeckel.eu>

Signed-off-by: Steffen Jaeckel <s@jaeckel.eu>

Signed-off-by: Steffen Jaeckel <s@jaeckel.eu>

Signed-off-by: Steffen Jaeckel <s@jaeckel.eu>

Signed-off-by: Steffen Jaeckel <s@jaeckel.eu>