Don't use <envar> in docs

Switch to simpler markdown, `foo`.
Don't use <filename> in docs

Switch to simpler markdown, `foo`.
Convert external links to markdown syntax
Updated Thai translation
GOption: fix bug in strv mode

We are a bit too aggressive about freeing memory in strv mode.  Only
free it in the case that we actually set the pointer to NULL.

Uncovered by the GApplication tests.
GApplication: parse command line options

Add support for parsing command line options with GApplication.

You can add GOptionGroup and GOptionEntry using two new APIs:
g_application_add_option_group() and
g_application_add_main_option_entries().

Also add a "handle-local-options" signal that allows handling of
commandline arguments in the local process without having to override
local_command_line.

As a special feature, you can have a %NULL @arg_data in a GOptionEntry
which will cause the argument to be stored in a GVariantDict.  This
dictionary is available for inspection and modification by the
"handle-local-options" signal and can be forwarded to the primary
instance in cases of command line invocation (where it can be fetched
using g_application_command_line_get_options()).

https://bugzilla.gnome.org/show_bug.cgi?id=721977
Use a code block instead of <screen>
Use markdown for images
Stop using starttag elements
Docs: don't use option tags
Docs: use quotes instead of firstterm
Docs: replace <literal> by `
Updated Brazilian Portuguese translation
Stop using <para> for ids

Instead, use the id support in markdown headings.
Stop using replaceable tags
Remove a few overlooked literals
Updated Galician translations
Updated Spanish translation
Eradicate links and xrefs

These are all replaced by markdown ref links.
Remove tables from GFileAttribute docs