doc: Convert man pages to AsciiDoc format

Manpages were available in troff format, which was inconvenient for
editing. This commit converts existing man pages to AsciiDoc format and
modifies the build system to generate man pages when building the source
using:

   a2x -f manpage <file>

Minor fixes, especially typos in the Copyright section, are also performed.

Change-Id: Ic7ac4c22ffcf8b8048d43f3844484350111ce45f