Add Meson build project file.

Example usage:

  # Configure Meson build in directory `build-meson` to generate
  # release binaries comparable to to the ones from the
  # autotools/make build system.
  meson setup build-meson \
        --prefix=/usr/local \
        --buildtype=debugoptimized \
        --strip \

  # After configuring the Meson build with the above command,
  # compile and install to `/usr/local/`; this includes a pkg-config
  # file.
  ninja -C build-meson install

  # Alternatively, compile and install to `/tmp/aa/usr/local/...`
  # for packaging.
  DESTDIR=/tmp/aa ninja -C build-meson install

  # Generate documentation under `build-meson/docs`.
  ninja -C build-meson docs

Library size comparison for stripped `` generated by
all three build systems:

  - Default build (autotools + libtool): 712 KiB
  - CMake build (RelWithDebInfo):        712 KiB
  - Meson build:                         712 KiB

* New top-level Meson build file for the library.

* meson_options.txt: New file.  It holds user-selectable options for
the build, which can be printed with `meson configure`, and selected
at `meson setup` or `meson --reconfigure` time with

* scripts/ A script invoked by `` to
parse `modules.cfg` and extract important information out of it
(i.e., the list of modules).

* scripts/ New script invoked by ``
to process the original `ftoption.h` file.  It enables or disables
configuration macro variables based on the available dependencies.
This is similar to what other build systems are using (i.e., Meson's
`configure_file()` command is not used here).

* scripts/ New script invoked by
`` to extract the FreeType version number from

* scripts/ New script invoked by
`` to extract the libtool `revision_info` data from
`builds/unix/configure.raw`, and to generate the corresponding
shared library suffix.

* scripts/ New script invoked by
`` to generate the FreeType 2 reference documentation
(using the `docwriter` and `mkdocs` packages, which must be already
9 files changed