docs: prevent smartphones from being too smart (docbook)

Add HTML <meta> tag to not auto-create telephone number links on mobile browsers also in docbook processed documents.

Reference: https://github.com/networkupstools/nut/issues/78

XSL files source:
- https://github.com/asciidoc/asciidoc/blob/master/docbook-xsl/common.xsl
- https://github.com/asciidoc/asciidoc/blob/master/docbook-xsl/xhtml.xsl
- https://github.com/asciidoc/asciidoc/blob/master/docbook-xsl/chunked.xsl
Add improved support for Eaton 5P

Add the necessary hooks to improve support for Eaton 5P range. This
includes post-processing of the model name, along with handling rules
for battery voltage (actual and nominal)
Closes #96: Install upsdrvctl to $prefix/sbin

Install upsdrvctl to $prefix/sbin rather than $driverexec. upsdrvctl has
been historically standing beside the drivers. It now resides in the
system binaries ($prefix/sbin) directory
Fix snmp-ups segmentation fault

A basic sanity check was missing in the core code of snmp-ups, causing
a driver crash under some specific circumstances, at driver
initialisation time. Hence, this does not affect production systems
Remove the generation of HAL support files

Remove the code supporting the generation of HAL FDI file. This is
the first commit of a set to address Github issue #99
OpenBSD ports tree patches for EPROTO

Closes networkupstools/nut#44
Remove the remaining HAL files and references

Remove the remaining build rules, source code and documentation related
to the FreeDesktop Hardware Abstraction Layer (HAL) support. For the
record, with this HAL implementation, NUT drivers were sending data
over DBus (Closes: #99)
Add a note on Hardware Abstraction Layer removal
Merge pull request #105 from networkupstools/hal_removal

Hal removal