Add explicit tests for division by zero to all user-accessible integer

division and modulo functions, to avoid problems on OS X (which fails to
trap 0 divide at all) and Windows (which traps it in some bizarre
nonstandard fashion).  Standardize on 'division by zero' as the one true
spelling of this error message.  Add regression tests as suggested by
Neil Conway.

src/test/regress/sql/errors.sql

@@ -17,7 +17,7 @@ select 1;
 --
 
 --
--- RETRIEVE
+-- SELECT
  
 -- missing relation name 
 select;
@@ -55,7 +55,7 @@ delete from nonesuch;
 
 
 --
--- DESTROY
+-- DROP
  
 -- missing relation name (this had better not wildcard!) 
 drop table;
@@ -65,9 +65,8 @@ drop table nonesuch;
 
 
 --
--- RENAME
+-- ALTER TABLE
  
-
 -- relation renaming 
 
 -- missing relation name 
@@ -112,7 +111,7 @@ end;
 
 
 --
--- DEFINE AGGREGATE
+-- CREATE AGGREGATE
 
 -- sfunc/finalfunc type disagreement 
 create aggregate newavg2 (sfunc = int4pl,
@@ -128,7 +127,7 @@ create aggregate newcnt1 (sfunc = int4inc,
 
 
 --
--- REMOVE INDEX
+-- DROP INDEX
  
 -- missing index name 
 drop index;
@@ -141,7 +140,7 @@ drop index nonesuch;
 
 
 --
--- REMOVE AGGREGATE
+-- DROP AGGREGATE
  
 -- missing aggregate name 
 drop aggregate;
@@ -163,7 +162,7 @@ drop aggregate newcnt (float4);
 
 
 --
--- REMOVE FUNCTION
+-- DROP FUNCTION
  
 -- missing function name 
 drop function ();
@@ -176,7 +175,7 @@ drop function nonesuch();
 
 
 --
--- REMOVE TYPE
+-- DROP TYPE
  
 -- missing type name 
 drop type;
@@ -252,3 +251,28 @@ drop instance rule nonesuch on noplace;
 -- no such rule 
 drop rewrite rule nonesuch;
 
+--
+-- Check that division-by-zero is properly caught.
+--
+
+select 1/0;
+
+select 1::int8/0;
+
+select 1/0::int8;
+
+select 1::int2/0;
+
+select 1/0::int2;
+
+select 1::numeric/0;
+
+select 1/0::numeric;
+
+select 1::float8/0;
+
+select 1/0::float8;
+
+select 1::float4/0;
+
+select 1/0::float4;