Compilation warnings due to conditionally defined values

[rafaelmds]

In some machines, the compiler warns about -Wmaybe-uninitialized variables.

This is caused by some variables whose values are conditionally defined, although a no-matching scenario is never to be expected.

So, this need some improvement to define a default value and some improvement in the series of if conditionals.

Some variables presenting this issue:

• dh_v_mod in Calc_dt_calor (main.cpp)
• temper_aux in Thermal_init_3d (DM1_3d.cpp)
• p_prox in Swarm_add_remove_2d (DMSwarm_move.cpp)
• p_prox_total and chosen in Swarm_add_remove_3d (DMSwarm_move.cpp)