Make Singularity a monster-only spell

As a player spell, it's problematic in various ways - reliably dealing damage
and being fully effective out of LOS and often preventing the monsters it
affects from being able to enter LOS at all. It also doesn't fit the
Translocations school thematically at all, being a pure damage spell, and with
the damage and out-of-LOS effects removed it wouldn't be very interestingly
distinct from other already-existing Tloc spells.

It remains as a random pan lord spell for now, but it might be better not to
keep the effect for such a rare case.

crawl-ref/source/book-data.h

@@ -297,7 +297,6 @@ static const vector<spell_type> spellbook_templates[] =
     SPELL_CONTROLLED_BLINK,
     SPELL_MALIGN_GATEWAY,
     SPELL_DISJUNCTION,
-    SPELL_SINGULARITY,
 },
 
 {   // Book of Debilitation

crawl-ref/source/spl-cast.cc

@@ -1063,9 +1063,6 @@ static targetter* _spell_targetter(spell_type spell, int pow, int range)
         return new targetter_fragment(&you, pow, range);
     case SPELL_FULMINANT_PRISM:
         return new targetter_smite(&you, range, 0, 2);
-    case SPELL_SINGULARITY:
-        return new targetter_smite(&you, range, singularity_range(pow, 2),
-                                                singularity_range(pow));
     case SPELL_DAZZLING_SPRAY:
         return new targetter_spray(&you, range, ZAP_DAZZLING_SPRAY);
     case SPELL_EXPLOSIVE_BOLT:
@@ -1869,9 +1866,6 @@ static spret_type _do_cast(spell_type spell, int powc,
     case SPELL_FULMINANT_PRISM:
         return cast_fulminating_prism(&you, powc, beam.target, fail);
 
-    case SPELL_SINGULARITY:
-        return cast_singularity(&you, powc, beam.target, fail);
-
     case SPELL_SEARING_RAY:
         return cast_searing_ray(powc, beam, fail);
 
@@ -1900,6 +1894,7 @@ static spret_type _do_cast(spell_type spell, int powc,
     case SPELL_LETHAL_INFUSION:
     case SPELL_POISON_WEAPON:
     case SPELL_SEE_INVISIBLE:
+    case SPELL_SINGULARITY:
     case SPELL_SONG_OF_SHIELDING:
     case SPELL_SUMMON_SCORPIONS:
     case SPELL_SUMMON_ELEMENTAL:

crawl-ref/source/spl-data.h

@@ -1658,7 +1658,7 @@ static const struct spell_desc spelldata[] =
 {
     SPELL_SINGULARITY, "Singularity",
     SPTYP_TRANSLOCATION,
-    SPFLAG_GRID | SPFLAG_AREA | SPFLAG_NOT_SELF,
+    SPFLAG_GRID | SPFLAG_AREA | SPFLAG_NOT_SELF | SPFLAG_MONSTER,
     9,
     200,
     LOS_RADIUS, LOS_RADIUS,