Start with a level 1 spell and enough power

Ensure the first spell - if any - given to the hero in initial
inventory is level 1 - otherwise you can end up with a situation
where the hero knows level 3 spells, but won't have enough power
to cast them.

If the hero starts out with a spell, ensure enough power (5)
to cast that level 1 spell.

include/extern.h

@@ -2539,6 +2539,7 @@ extern void initialspell(struct obj *);
 extern boolean known_spell(short);
 extern int spell_idx(short);
 extern boolean force_learn_spell(short);
+extern int num_spells(void);
 
 /* ### steal.c ### */