pcre2_jit_stack_create() allows the user to indicate how big of a
stack size JIT should be able to allocate and use, using a size_t
variable which should be able to hold bigger values than reasonable.

Internally, the value is rounded to the next 8K, but if the value
is unreasonable large, would overflow and could result in a smaller
than expected stack or a maximun size that is smaller than the
minimum..

Avoid the overflow by checking the value and failing early, and
while at it make the check clearer while documenting the failure
mode.

Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>

* test: avoid failing RunTest if pcre2test -S is not supported

If `pcre2test -S` is not supported then then avoid checking for it
in a test.

There is already a conditional check for it to be used when it is
needed and it is available, so adjust that as well.

* pcre2test: update list of platform support for -S

Minix 3 has a BSD userspace and now works fine, but Haiku still
doesn't support stack limits, so update accordingly.

To allow pcre2grep to do an early exit in a resumable way, -m uses
fseek on stdin, which is sadly not supported in several platforms.

Most of the conflicting issues come from the fact that managing the
position while buffering is not trivial, and is therefore an optional
feature[1] of POSIX.1-2017

Workaround this by removing the buffer to stdin, if the -m option is
being used.  There is likely not a significant performance benefit
even for the platforms that support it, but it could be conditionally
added in that case, later.

Fixes: #10

[1] https://pubs.opengroup.org/onlinepubs/9699919799/functions/fseek.html

* tests: use a explicit filehandle to share in testing -m

The way stdin is shared to all participants of a subshell varies
per shell, and at least the standard /bin/sh in Solaris seem to
create a new copy for each command, defeating the purpose of the
test.

Use instead exec to create a filehandle that could then be used
explicitly in the test to confirm that the stream is set.

* pcre2grep: correctly handle multiple passes

When the -m option is used, pcre2grep is meant to exit after enough
matches are found but while leaving the stream pinned to the next position
after the last match.

Unfortunately, it wasn't tracking correctly the beginning of the stream
on subsequent passes, and therefore it will fail to use the right seek
value.

Grab the position of the stream at the beginning and while at it, make
sure that the stream passed hasn't been consumed already.

* jit: allow building with ancient MSVC versions

Visual Studio older than 2013, fails to build with JIT enabled,
because it is unable to parse non C89 compatible syntax, with
mixed declarations and code.

While most recent compilers wouldn't even report this as a warning
since it is valid C99, it could be also made visible by adding to
gcc/clang the -Wdeclaration-after-statement flag at build time.

Move the code below the affected definitions.

* pcre2grep: avoid mixing declarations with code

Since d5a61ee8 (Patch to detect (and ignore) symlink loops in
pcre2grep., 2021-08-28), code will fail to build in a strict C89
compiler.

Reformat slightly to make it C89 compatible again.

* cleanup: remove references to no longer used stdint.h

Since 19c50b9d (Unconditionally use inttypes.h instead of trying for
stdint.h (simplification) and remove the now unnecessary inclusion in
pcre2_internal.h., 2018-11-14), stdint.h is no longer used.

Remove checks for it in autotools and CMake and document better the
expected build failures for systems that might have stdint.h (C99)
and not inttypes.h (from POSIX), like old Windows.

* cleanup: remove detection for inttypes.h which is a hard dependency

CMake checks for standard headers are not meant to be used for hard
dependencies, so will prevent a possible fallback to work.

Alternatively, the header could be checked to make the configuration
fail instead of breaking the build, but that was punted, as it was
missing anyway from autotools.

Visual Studio 2013 includes support for %zu and %td, so let newer
versions of it avoid the fallback, and while at it, make sure that
the first check is for DISABLE_PERCENT_ZT so it will be always
honoured if chosen.

prtdiff_t is signed, so use a signed type instead, and make sure
that an appropiate width is chosen if pointers are 64bit wide.

Remove the need for the size_t cast and instead change the size
of the equivalent format identifier to avoid truncations.

Documentation update.

Fix option name in pcre2convert docs

Fix incorrect detection of alternatives in first character search.

38653).

re-enable the old behaviour, just in case.