Fix (workaround) for Landmine does almost no damage

[Firestorm01X2]

Fix (workaround) for Landmine does almost no damage

Summary

Bugfixes #60

Purpose of change

Fixes #60

Describe the solution

Connected issue:
CleverRaven/Cataclysm-DDA#37724

I believe you should check function trapfunc::landmine() at src/trapfunc.cpp:L605
It clearly uses same explosion() function but uses preset values so I think that landmine probably does not use JSON set values at all.

Confirmed. Landmine triggers:

bool trapfunc::landmine( const tripoint &p, Creature *c, item * )
{
    // tiny animals are too light to trigger land mines
    if( c != nullptr && c->get_size() == MS_TINY ) {
        return false;
    }
    if( c != nullptr ) {
        c->add_msg_player_or_npc( m_bad, _( "You trigger a land mine!" ),
                                  _( "<npcname> triggers a land mine!" ) );
    }
    explosion_handler::explosion( p, 18, 0.5, false, 8 );
    g->m.remove_trap( p );
    return true;
}

Explosive triggers with hardcoded values.

For now lets set explosion data to adequaete values. Used values from greande explosion.
Applied to boody trap as well.

Describe alternatives you've considered

Testing

1. Set a mine
2. Step on a mine
3. Observe damage. It should be comparable to grenade explosion. Previosly it barely did any damage due bug.

Additional context

[Coolthulhu]

Functions only used in one file should be declared static.
You may need to move it above the places it is invoked in.