Fix display bug in menues/listings:

Use function calcStartPos to calculate the display offset (first line of the menu to be printed).
It incorporates the option MENU_SCROLL and does the actual calculation correctly, the calculation in construction.cpp was missing the offset=0 case.
Print npcs & notes and vehicle names on overmap in one step

Instead of having three nearly identical functions, add note, npcs names and vehicles names to a vector and print that vector line by line.
Also uses utf8_width for each line (not used previously for npc names and vehicle names).

Removed overmap::print_vehicle and overmap::print_npcs.
Moved overmap::has_vehicle to overmapbuffer.
Remove storing and restoring old data values in defense games.

That data is reloaded whenever the user starts a new game anyway (as it's part of the world data, probably altered by mods).

Also remove `(void)g` - old artifacts of a simpler time when g was parameter to those functions.
Truncate the mod names in the mod selection window.

Extracted display of the two lists into a function, called for both lists.
Truncate the mod name with the utf8_truncate function, don't use fold_and_print there.
Fix long option names / values wrapping onto next line.

Uses utf8_truncate to truncate long strings.
Defense game mode: initialize members on style DEFENSE_EASY

Previously the DEFENSE_EASY style would bypass initialization of many members.

Moved the default entries in the swtch statements out of the switch
statement. Behaviour is unchanged, but in case someone adds a
style/location, the compiler will warn about a missing case entry.
Remove obsoleted rule in Makefile.

SDLMain.o is no longer needed since SDL2 does not use it.

The file SDLMain.m which is required for this rule does not exist since 2bd95404f0654d72d8f93bed883020cfa7dced1b
Fix description of keybindings of mod selection tab:

'+' and '-' are used to move the mods up/down in the list of selected mods.
CONFIRM (enter key) is used to activate or deactivate the mod (depending on which list is active).
Redraw the mod selection screen after the help screen has been visited.