As part of the refactor, have the sources include the public headers via
the libx52 prefix, instead of relying on the include directories
approach in meson.build
The autotools build infrastructure was deprecated back in 0.3.3, and any
bugs in the Meson build infrastructure have been fixed now. This
eliminates the legacy build scripts which were hard to maintain.
Meson is a far more robust build framework, compared to autotools. This
greatly simplifies adding new features, since it's far easier to
maintain a set of meson.build files vs the autotools mishmash.
DEPRECATION NOTICE: Autotools based build is deprecated and will be
removed in the future.