Clean up build process & update chdkptp to r962

[a-hurst]

This PR cleans up the overall chdkptp.so build process and updates the included chdkptp revision to r962, which matches the latest official binaries from the project.

First, this removes the chdkptp git submodule (which is stuck on an ancient version due to the closure of svn2github) and replaces it with a python script that grabs and unarchives a Zip of the source code straight from the project's SVN repo. This removes the need for SVN or submodules entirely and should make the process of updating the chdkptp revision much easier in the future.

Next, this updates the bundled chdkptp to r962 and updates the patchfile accordingly. 962 was used instead of the latest release to minimize the likelihood of breaking things while still using a more modern version.

Finally, to simplify the build process and remove the build requirement of Lua 5.2 or 5.3 (not available on current versions of Fedora and likely other distros as well), this PR uses chdkptp's own setup-ext-libs.bash script to download, build, and link to a static version of Lua 5.2 when building chdkptp. Making this work also requires modifying the Lua build script to compile with -fPIC enabled, since we're linking to it from a shared library instead of a standard binary like usual.

[a-hurst]

Whoops, meant to open this as a PR on my own fork! Leaving this up in case this project ever gets maintained again.