Add blame to libgit

Rather than duplicate large portions of builtin/blame.c in cgit, it would be better to shift its core functionality into libgit.a. The functionality left in builtin/blame.c mostly relates to terminal presentation.

Since RFC v2 patchset:
Rebased (merged in timestamp_t changes) Reorganized to split out and group 'mechanical' changes

Jeff Smith (29):
blame: remove unneeded dependency on blob.h
blame: move textconv_object with related functions
blame: remove unused parameters
blame: rename origin structure to blame_origin
blame: rename scoreboard structure to blame_scoreboard
blame: rename origin-related functions
blame: rename coalesce function
blame: rename ent_score function
blame: rename nth_line function
blame: move stat counters to scoreboard
blame: move copy/move thresholds to scoreboard
blame: move contents_from to scoreboard
blame: move reverse flag to scoreboard
blame: move show_root flag to scoreboard
blame: move xdl_opts flags to scoreboard
blame: move no_whole_file_rename flag to scoreboard
blame: make sanity_check use a callback in scoreboard
blame: move progess updates to a scoreboard callback
blame: wrap blame_sort and compare_blame_final
blame: rework methods that determine 'final' commit
blame: create scoreboard init function
blame: create scoreboard setup function
blame: create entry prepend function
blame: move core structures to header
blame: move origin-related methods to libgit
blame: move fake-commit-related methods to libgit
blame: move scoreboard-related methods to libgit
blame: move scoreboard setup to libgit
blame: move entry prepend to libgit

 Makefile           |    1 +
 blame.c            | 1863 +++++++++++++++++++++++++++++++++++++++++++++
 blame.h            |  175 +++++
 builtin.h          |    2 -
 builtin/blame.c    | 2130 ++--------------------------------------------------
 builtin/cat-file.c |    1 +
 diff.c             |   23 +
 diff.h             |    7 +
 8 files changed, 2143 insertions(+), 2059 deletions(-)
 create mode 100644 blame.c
 create mode 100644 blame.h

2.9.3