Add () and {} key maps to navigate to the previous and next file or hunk in the diff. This required changing Got's diff API to collect line type metadata in addition to the line offsets already produced as prompted by stsp. ok stsp@

Make the choice of diff algorithm configurable by diff API users. The got and gotweb programs keep using Patience diffs which are prettier than Myers. But tog should be as fast as possible since it is being used interactively. If performance of Patience diff gets improved later we can consider switching tog back over to it. ok tracey jamsek

ok tracey

Saves us from doing a malloc/free call for every item on the list. ok op@

ok millert, naddy

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.

this will need to be reworked later. ok stsp

These headers were implicitly used on OpenBSD, but building on Linux revealed that <time.h> wasn't included directly. diffreg.c uses ctime(), which additionally needs <sys/types.h>.