Fix location handling for figures
Improve BOL error reporting
Improve error reporting from bol_space()
Improve BOL errors for items
Improve BOL error messages
Fix auxiliary node creation
Fix buffer node creation

The previous code assumed that we were ever only creating one buffer at
a time.  While strictly true, we need to textify that buffer before we
continue on the next one.  This was done, but if we encounter a group, a
new buffer may be created, in which case we won’t textify until it’s too
late.  We now keep track of the buffer node so that we may textify it
whenever we start to build a new buffer.
Clear anchors before each section and at end of document
Allow freeing anchors without children
Fix error concatenation
Support FILE argument
Update Autoconf/Automake version dependencies
Call nml:adjust-uri for image URIs
Update man page with new command-line interface
Fix groff escaping
Improve man page rules
Fix error output format
Add gitattributes for README
Update README with installation instructions, etc.