manuals: generate vty reference xml at build time

Move 'doc' subdir further down to "make sure" the osmo-hlr binary is built
before the docs.

Remove hlr_vty_reference.xml from the source tree.

In manuals/Makefile.am use the new BUILT_REFERENCE_XML feature recently added
to osmo-gsm-manuals, and add a build target to generate the XML using the new
osmo-hlr --vty-ref-xml cmdline switch.

Depends: I613d692328050a036d05b49a436ab495fc2087ba (osmo-gsm-manuals)
Change-Id: I99e61274e2ceb2c1fe5fb05bb99e1ec19695ad92
3 files changed