When rendering the contents of the GLib documentation stored inside the
introspection data, a common behaviour is to take the first paragraph as
a summary of the symbol being documented.

The documentation is assumed to be in Markdown format, which means:

 - paragraphs must be separated by newlines
 - lines that have an indentation of four or more spaces are considered
   code blocks
 - lines that start with a `#` are considered titles

This means we need to slightly tweak the documentation in our sources to
ensure that it can be rendered appropriately by tools that are not
gtk-doc.

See issue: #2365

Add more GIR annotations to gparam.c and gsignal.c

See merge request GNOME/glib!1804

Instead of collecting more pspecs than we need, just don't add them to
the list(s) in the first place.

Fix more warnings

See merge request GNOME/glib!1773

gobject/gparam.c: In function ‘g_param_type_register_static’:
gobject/gparam.c:1434:3: error: missing initializer for field ‘value_table’ of ‘GTypeInfo’ {aka ‘struct _GTypeInfo’}
 1434 |   };
      |   ^
In file included from gobject/gvalue.h:26,
                 from gobject/gparam.h:26,
                 from gobject/gparam.c:26:
gobject/gtype.h:1063:26: note: ‘value_table’ declared here
 1063 |   const GTypeValueTable *value_table;
      |                          ^~~~~~~~~~~

`GParamSpec`s are floating by default.

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>

This commit only looks at the `Returns:` lines in the documentation, and
has examined all of them in the file. Function arguments have not been
checked.

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>

Helps: #2227

This was mostly machine generated with the following command:
```
codespell \
    --builtin clear,rare,usage \
    --skip './po/*' --skip './.git/*' --skip './NEWS*' \
    --write-changes .
```
using the latest git version of `codespell` as per [these
instructions](https://github.com/codespell-project/codespell#user-content-updating).

Then I manually checked each change using `git add -p`, made a few
manual fixups and dropped a load of incorrect changes.

There are still some outdated or loaded terms used in GLib, mostly to do
with git branch terminology. They will need to be changed later as part
of a wider migration of git terminology.

If I’ve missed anything, please file an issue!

Signed-off-by: Philip Withnall <withnall@endlessm.com>

The various `g_strdup_printf()` returns values in the implementations of GValue
lcopy_func are runtime checks which could be disabled if one wants and therefore
should be handled as such with g_return_val_if_fail()

Signed-off-by: Philip Withnall <withnall@endlessm.com>