Add native Linux Meson build support

[Copilot]

PCRE2 lacks an upstream-native Meson build, leaving Meson consumers dependent on an external adapter that can drift from the CMake configuration. This introduces a Linux-first Meson port aligned with CMake’s option names, defaults, ordering, and feature set.

Changes

• Configuration

  • Mirrors CMake build options and validation rules.
  • Parses project and ABI versions from configure.ac.
  • Adds platform, compiler, JIT, visibility, and linker probes.
  • Generates config.h, public headers, character tables, and symbol maps.

• Targets

  • Builds independent static/shared 8-, 16-, and 32-bit libraries.
  • Adds the POSIX wrapper, pcre2grep, test executables, and fuzz targets.
  • Exposes canonical Meson dependencies such as libpcre2-8.

• Packaging

  • Installs headers, libraries, tools, manpages, and HTML/text documentation.
  • Generates pkg-config files, pcre2-config, and CMake package metadata.

• Documentation

  • Adds Meson setup and subproject integration guidance.
  • Records Linux-first limitations and design choices for review.

meson setup build-meson \
  -DBUILD_SHARED_LIBS=true \
  -DPCRE2_BUILD_PCRE2_16=true \
  -DPCRE2_SUPPORT_JIT=AUTO
meson compile -C build-meson
meson test -C build-meson

[NWilson]

!!!! I am not planning on doing this immediately.

However - writing a build script is a sort of task that AI can (sometimes) be quite good at.

I asked GPT Sol to have a go. This is what it produced.

It won't be merged anytime soon, but potentially it's an option.

See #853