More OSS-Fuzz support

[wiredfool]

Changes proposed in this pull request:

• Delegate build.sh, build-dictionaries to Pillow. This requires a further commit in oss-fuzz after this merges to master
• Add a fuzzer for font files. This opens truetype files and performs some basic operations with them.
• Refactor and add tests for the fuzzers. This should catch any cases of the fuzzers totally failing with unexpected errors, but we are still expecting that there are a reasonable number of exceptions thrown due to attempting to load broken input.
• Lint fixes

[wiredfool]

Test failure appears to be unrelated.

[radarhere]

Suggested change

	if not path or b"LICENSE.txt" in path or b".pil" in path:
	if not path or path.endswith(b"LICENSE.txt") or path.endswith(b".pil"):

[radarhere]

Suggested change

	pytest.skip("Fuzzer is linux only", allow_module_level=True)
	pytest.skip("Fuzzer is macOS and Linux only", allow_module_level=True)

[wiredfool]

Well, technically, it's linux only, but the required bits don't fail on osx because it includes the find command.

[radarhere]

Suggested change

	"path", subprocess.check_output("find Tests/fonts -type f", shell=True).split(b"\n")
	)
	def test_fuzz_fonts(path):
	if not path:
	return
	"path", subprocess.check_output("find Tests/fonts -type f", shell=True).strip().split(b"\n")
	)
	def test_fuzz_fonts(path):