Use the global variable only when needed and add an initializer for it
in the default options.

Use a GCC pragma to disable -Wmissing-field-initializers in this file.
This works with both GCC and CLang, and should be harmless on other
compilers since unknown pragmas are supposed to be ignored.

Old implementation was not really fitting the updating needs and had a
bug making symbols disappear if they haven't changed but their parent
did (e.g. when a C++ constructor's signature changed).

New implementation does:
1) walk old tree, updating or removing rows;
2) add remaining tags.

It walks less than (new_tags + old_tags + new_tags) in the worst case,
thanks to some hash table-based caching;  and also gets rid of the
"valid" column in the symbols tree, saving a few bytes in memory.

Finally, there is a ~7% performance gain (from 21 to 18ms) upon common
tree updates, sometimes more.

This is especially useful if tab close buttons are disabled.

Instead we should use that tab which is under mouse cursor where the user clicked (this might be a
different one than the current document). To be able to do so, we need to handle the right-click signal
per tab not on the GtkNotebook tab area to identify the tab under the mouse cursor.

While this is a violation of the C standard in theory, it should not affect anything.
Anyway, removing the double underscores makes the header guard scheme more
consistent with the rest of Geany header files so it's still a good thing.

When removing the last leaf of a symbols tree branch, make sure not
to start walking parent's children again.

Cleanup 'Go to tag' sections and keybinding descriptions.

This does not affect existing users.

Ctrl-T          Go to tag definition
Ctrl-Shift-T    Go to tag declaration

A default keybinding for 'Transpose current line' is no longer
necessary as it does the same as 'Move line(s) up', which we now have
a default for.

This does not affect existing users.

Ctrl-Shift-PageUp   Move document left
Ctrl-Shift-PageDown Move document right

The above shortcuts were aliases for selecting left/rightmost
documents, but those are not necessary as Alt-1/Alt-0 does the same.

Alt-PageUp      Move line(s) up
Alt-PageDown    Move line(s) down

Alt is easier to press than Ctrl-Shift, so is better for moving lines
as this needs more accuracy.

This adds a new commandline option --read-only (or -r). It's implemented
according to the behavior agreed on on the mailing list:

--read-only applies to all files on the command line
irrespective of positioning and has no effect on any other files
opened by session or menu (...)

Current behaviour on attempting to re-open a file with different
read-only status is that nothing happens, the already open
file is raised but not changed. (...)

It actually happens, and until fixing this properly, don't output
useless useless scary warnings.  Anyway, this is not a big problem
or anything.

This adds an hidden VTE preference, send_cmd_prefix, that allows to
define a prefix for the commands Geany sends to the shell in the VTE
like "cd" when following current path.

This can be used for example to prevent some shells (Bash, ZSH, maybe
others) from putting these commands in the history by setting this to
a space.

Geany saves the path for each active plugin on shutdown, but the 3
valid plugin paths can each change.

SETPTR makes it clear that a macro is being used in code.
Restore setptr without do/while in case of use without semi-colon.

Note: This doesn't affect existing user shortcuts.

Ctrl-Shift-D    Find Document Usage
Ctrl-Shift-E    Find [Session] Usage (one letter after doc usage and
                close on the keyboard)

These are standard shortcuts for browsers:
Alt-Right   Forward
Alt-Left    Back

This matches the build/make symmetry for compile (F8):
Shift-F8    Make Object

Use do {...} while (0) instead of {...}.
Document the order of events and purpose of setptr properly.

E.g.
highlighting.c:950:3: error: the address of
'highlighting_styles_ADA' will always evaluate as 'true'

Note: This commit also contains some trailing whitespace removal.

Print the GError message if the users filetype extract regex does
not compile.

* Never try to do a regex match on a NULL string;
* Don't try to unref a possibly NULL regex.

Works around the issue discussed in commit 1e54fb6a by using the file
chooser's property accessor function.
Rename on_file_notify() to better explain its purpose.

In the dialog, the plugin's description is more interesting and useful than the full filename.
Instead, show the filename in the bottom box for those interested in.

This should avoid confusion in the toolbar customize dialog to not have
two identical named items.

Based on a patch from Elias Pschernig, thanks.
Parser was taken from upstream CTags.

Closes patch#3325139.