Throwing this into the mix for a while, we can always get rid of it again if it becomes annoying. No objections from stsp@

ok stsp@

This new diff implementation was started by Neels Hofmeyr during the u2k20 hackathon and now replaces diffreg.c code lifted from the OpenBSD base system. The integration of this code into Got was done by me. Got now uses the patience diff algorithm by default. The diff.git repository will remain the primary repository for the diff code, which already compiles and runs on other operating systems such as Linux. Any fixes and improvements for files inherited from the diff.git repository should be written against that repository and synced to got.git afterwards.

sthen@ suggested to drop -Werror; I think we don't need any -W in release mode

Compile static libexec binaries for gotweb, keeping them separate from the main build. Use the same source files but a separate set of Makefiles. Previously, 'make web-install' installed whichever libexec binaries had already been built, and if those happened to be dynamically linked they failed to run inside the chroot which resulted in "privsep peer process closed pipe" being rendered on the index page.