Deny skill exercise if not enough available xp (mesilliac).

Patch 1744207. Should be easy enough to revert if it doesn't work
out, and seems quite independent from other 0.6 changes. From the
request:

  After a while of playing i found that available xp for
  exercising skills decreases to zero quickly after gaining it.
  It means most skills don't get excercised unless you usually
  use them right after fighting.

  I hacked my version to randomly deny a skill exercise if you
  don't have much available xp. The chance is available xp /
  total xp needed this level. Seems to work well - skills are
  getting exercised more evenly and it finds its own equilibrium.
  You can still do something repeatedly to practice its skill,
  just you don't have to do it immediately after killing a
  powerful monster.

1 files changed, 7 insertions, 0 deletions

diff --git a/crawl-ref/source/skills.cc b/crawl-ref/source/skills.cc
index d39635531a..66d6adb6c2 100644
--- a/crawl-ref/source/skills.cc
+++ b/crawl-ref/source/skills.cc
@@ -150,6 +150,13 @@ int exercise(int exsk, int deg)
         if (you.exp_available <= 0 || you.skills[exsk] >= 27)
             break;
 
+        // randomly deny skill excercise if not many points available
+        if (random2(you.exp_pool_cutoff()/10) >= you.exp_available)
+        {
+            deg--;
+            continue;
+        }
+
         if (you.practise_skill[exsk] || one_chance_in(4))
             ret += _exercise2( exsk );