Standardized makefile and c bindings

[mattmassicotte]

In #111 @krzyzanowskim added a Makefile and C bindings. These differed from the original "standard" version, but were better in many ways. I used this version as a template to fix up the existing Makefiles in other parsers, and in the process made just a few changes. I'm now moving those back here.

• Uses more built-in make functions
• Correctly assigns the parser URL in the pkgconfig file
• Treats the .pc file as a build artifact, just the .h
• Changes the header name from tree_sitter/tree-sitter-swift.h to tree_sitter/swift.h

The last one does have the potential to cause issues. But, it seems worth standardizing the header name to match other how other parsers do it.

I will coordinate a fix for https://github.com/krzyzanowskim/tree-sitter-xcframework, so I expect problems to be minimal.

[alex-pinkus]

Thank you for doing this! I’ll try to find time to take a look tomorrow.

[mattmassicotte]

No rush at all - thanks for putting up with all the churn!