Make numrun012 work with excess-precision.(#5856)

Remove exact base 2 logarithms, since their values depend on whether
excess precision is used or not (see also #5165).

MERGED from commits 5774835f and
19fc8e32.

tests/numeric/should_run/numrun012.hs

@@ -30,6 +30,6 @@ log2 x = ceiling log_x
           log_x = logBase 2 (fromIntegral (max 1 x))
 
 vals = [1, 2, 17, 259, 1000, 10000,
-        2^30 + 9000, 2^31 - 1, 2^31, 2^31 + 1,
-        2^32 - 1, 2^32, 2^32 + 1]
+        2^30 + 9000, 2^31 - 1, 2^31 + 1,
+        2^32 - 1, 2^32 + 1]
 

tests/numeric/should_run/numrun012.stdout

-[0,1,5,9,10,14,31,31,32,32,32,32,33]
+[0,1,5,9,10,14,31,31,32,32,33]
 -2.147483648e9
 -2.1474836e9
 -2.147483648e9

tests/numeric/should_run/numrun012.stdout-ws-64

-[0,1,5,9,10,14,31,31,32,32,32,32,33]
+[0,1,5,9,10,14,31,31,32,32,33]
 2.147483648e9
 8589934592
 2.1474836e9