Fixes warnings on versions of Linux where mallinfo(3C) has
been deprecated.

Clang 11 has either learned to inline find_stack_direction(), or it may
have inlined find_stack_direction() before but changed allocation order
for our "objects with automatic storage duration" that we use to check
the stack direction.

Calling find_stack_direction() through a volatile function pointer
should reliably prevent it from getting inlined and thus flush out the
real stack direction.

Thanks to Cezary Cerekwicki <ccerekwicki@opera.com> for the report.

The prototype is not available with _POSIX_C_SOURCE.

configure: add --with-exclude-site-prefixes option which excludes a path from being used for bin/lib/incudes

/opt/local on MacOS X can contain libraries that conflict with and
are incompatible with the system libraries (eg libiconv.dylib).
This has a tendency to break stuff.

If you need /opt/local, please use --with-site-prefixes.

Fixes linking with MariaDB and MySQL.

Setting the window size should now work.

Preparation for supporting ptys on NT.

Attempt to use paxctl to alter the PaX flags for the pike binary
to allow for generation of machine code.

Note that paxctl on NetBSD and Linux are incompatible.

Adds variant using timezone/altzone (eg Solaris).

Fixes the fallback implementation (using gmtime(3F)) to not
drift by an hour when the local time zone has tm_isdst == 1.

The ioctl-based /proc API was obsoleted in Solaris 2.6 (July 1997),
but to be supported "until the next major release". In Solaris 11.4
(August 2018) the support has now finally been removed.

Most of the removed code was from 1995, and was thus older than Pike...

Configure should now detect working == some correctly on Solaris.

On Solaris getcwd(NULL, x) only works if x is > 0.

Fixes building issues on Solaris.

Also consolidates the two implementations.

The LDSHARED test attempted to link the shared object with crt1.o,
which failed due to relocation errors. As we don't want to link
with the startup files anyway, make sure to ask gcc to not do it.

The previous patch broke the AC_CHECK_SIZEOF-tests when using
a non-default ABI.

Fixes compiler propagation to sub-configures when eg compiling
--with-abi.

Solaris 11 installs the header files for gmp and mpfr in sub-
directories of /usr/include/, but it also installs corresponding
pkg-config files. Use pkg-config to adjust the search paths so
that the following configure tests can find the header files.

when the defaults are better (+3% on average on pike -x benchmark on
MBP Core i7).

Also avoid -read_only_relocs since it's not applicable on 64-bit ABI.

deprecated on OS X.

depend on HAVE_FUNCTION_ATTRIBUTES being available, and the configure test
refused to set that if it detected __declspec before.

Running uncached configure with rntcl et al takes considerable time...