gui2/tcustom_tod: Don't redraw on slider updates if display_ not set
gui2/tcustom_tod: Remove direct call to gui2::twindow::draw()

It's unnecessary, results in a noticeable performance penality when
updating ToD color shift sliders, and the documentation says it's not to
be called directly (which raises the question of why it's a public
method in the first place).
gui2/tcustom_tod: Avoid having display::draw() commit the framebuffer

This allows the dialog to be redrawn on top of the updated display
contents once we are done without any flickering, and performance is
much better because this results in the framebuffer being committed once
instead of twice every time ToD color shift slider events are processed.
Use gui2::show_message instead of GUI1 to notify failed unit search
Revised text displayed in the failed unit search notification popup

 * Replaced straight apostrophes with Unicode apostrophes
 * Expanded contractions
gui2/tchat_log: Regroup navigation controls in subgrids

This should allow for fine-grained layout control.
Fix off-by-one buffer overrun in get_exe_dir

Found by coverity
Fix an off-by-one past-the-end buffer read in lua

Found by coverity
Fix invalid array index

Found by coverity
Fix some uninitialized variables, replace by NULL

Found by coverity
Don't leak empty labels

Found by coverity
ai_helper.put_labels: display content of strings rather than 'nan'
ai_helper: add functions to get direction indices and strings

These consist of a number of supplementary functions, plus three
function get_cardinal_directions, get_intercardinal_directions and
get_hex_facing which return strings for the directions (in cartesian or
hex coordinates) between two hexes.
Refactored the hotkeys system.
Made hotkey refactoring compile with cmake.
Update Xcode project file with hotkeys refactoring changes
Resolve includes to match the hotkey refactoring.
Updated Dutch translations
Updated changelog and players_changelog
Remove blank lines

Trying to get the formatting to be at least somewhat consistent.