Log Message:
Updated ninja-build to 1.7.2.

This is a minor release after v1.7.1, mostly bugfixes.

== Release notes.

* %e and %r work again in dumb terminals (#1146, #1148)
* `-t browse` now HTML-escapes rule names (#1157)
* an edge may now have 0 explicit outputs if it has implicit outputs (#1159)
* make misc/measure.py python 3-compatible
* misc/write_fake_manifest.py now optionally writes source files, use it to
  quickly produce large, buildable projects for testing (#1109, #1198)
* on newer FreeBSDs, use ppoll()