Initial support for saving settings to config.ini

Supported settings:
* currency
* measurement_format
* temperature_format
* sound_quality
better struct packing for MinGW
save_prompt actually opens save dialog
add initial s6 structure
Merge branch 'testing' of https://github.com/anyc/OpenRCT2 into anyc-testing
Merge branch 'anyc-testing'
fix award window bug and clean reset history
edge_scrolling and forced_software_buffering can now be edited ingame.

* edge_scrolling
* forced_software_buffering
New setting: always_show_gridlines.
add note about debugging routines
New setting: landscape_smoothing
New setting: show_height_as_units
New setting: save_plugin_data
Merge pull request #156 from kevinburke/top-toolbar-note

add note about debugging routines
Merge branch 'config-save-ini' of https://github.com/atmaxinger/OpenRCT2 into atmaxinger-config-save-ini
fix warnings
Merge branch 'atmaxinger-config-save-ini'