Fix regression making diff parsing fail when opening the blame view
Fix regression in diff_get_lineno
Fix regression in add_line_at making line numbers start atf 0 instead of 1

This in turn caused the stash view to segfault when displaying IDs.
Merge the content of BUGS into the README file
Use .adoc as the extension for AsciiDoc files in doc/
Rename README, INSTALL, and NEWS to end in .adoc

Add inter-document links to work on Github.
Fix and improve inter-document linking
Fix clean rule to remove DocBook XML files in doc/