pwkit/ninja_syntax.py: import from Ninja
pwkit/ninja_syntax.py: import from Ninja

This is a straight copy of the 'ninja_syntax' module provided by the Ninja
build system. They provide a 'ninja_syntax' module on PyPI but I'd rather just
bundle it here for convenience.

This version is from commit 97e9628 of
https://github.com/ninja-build/ninja/:misc/ninja_syntax.py . It appears to be
licensed under the Apache 2.0 License.

pkgw/pwkit