Description: Fix building POD-generated man pages.

This patch fixes / improves various bits:

• Provide a clean target for generated man pages.
• Don't use 'install' command that changes file permissions during build target (we might not have root privileges during build).
• Fix variable that gets checked during man page generation ($${suite}} vs. $${section}} in case statement.
• During parallel DEB builds (4 cores) it happened that the pod2man run wasn't finished when the install_man target started compressing the man page. Add a dependency between install_man and build_pod2man (although in d/rules these should run as independent Makefile calls).