Merge remote-tracking branch 'remotes/berrange/tags/docs-pull-request' into staging

docs: add docs about use of automatic cleanup functions

This is ostensibly about adding docs for the g_autofree/g_autoptr
macros. As part of doing that, however, the existing HACKING doc
is merged into the CODING_STYLE doc and the text is converted to
rst with a table of contents.

# gpg: Signature made Thu 05 Sep 2019 14:43:44 BST
# gpg:                using RSA key DAF3A6FDB26B62912D0E8E3FBE86EBB415104FDF
# gpg: Good signature from "Daniel P. Berrange <dan@berrange.com>" [full]
# gpg:                 aka "Daniel P. Berrange <berrange@redhat.com>" [full]
# Primary key fingerprint: DAF3 A6FD B26B 6291 2D0E  8E3F BE86 EBB4 1510 4FDF

* remotes/berrange/tags/docs-pull-request:
  docs: split the CODING_STYLE doc into distinct groups
  docs: document use of automatic cleanup functions in glib
  docs: merge HACKING.rst contents into CODING_STYLE.rst
  docs: convert README, CODING_STYLE and HACKING to RST syntax

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>