Implemented function to (un)highlight single line in buffer and used
that in nav.lua to prototype a moving line selection. Also commented out
an include in util.cpp that threw errors all of the sudden.
Function interface consitency: writeln_to_buf -> buf_writeln
NOTE: Included string.h again but clang will not compile this with glibc
2.20-3 from the arch repo. Downgraded to 2.20-2 for now.
Added prototype function for listing a directory to the main buffer but
it's not complete yet and won't do anything useful just yet. Also
removed some stuff from the buf struct that isn't being used and might
be implemented differently in the future if it is required.
Some more prototype functions for file system browsing were implemented.