Remove ALTER TABLE DROP until #3919 is resolved

NEWS.txt

@@ -72,6 +72,9 @@ Upgrading
       Also, the consistency level cannot be set in the language anymore, but is
       at the protocol level.
       Please refer to the CQL3 documentation for details.
+    - In CQL3, the DROP behavior from ALTER TABLE has currently been removed
+      (because it was not correctly implemented). We hope to add it back soon
+      (Cassandra 1.2.1 or 1.2.2)
 
 Features
 --------

doc/cql3/CQL.textile

@@ -324,7 +324,6 @@ bc(syntax)..
 
 <instruction> ::= ALTER <identifier> TYPE <type>
                 | ADD   <identifier> <type>
-                | DROP  <identifier>
                 | WITH  <option> ( AND <option> )*
 p. 
 __Sample:__
@@ -336,9 +335,6 @@ ALTER lastKnownLocation TYPE uuid;
 ALTER TABLE addamsFamily
 ADD gravesite varchar;
 
-ALTER TABLE addamsFamily
-DROP gender;
-
 ALTER TABLE addamsFamily
 WITH comment = 'A most excellent and useful column family'
  AND read_repair_chance = 0.2;
@@ -348,9 +344,9 @@ The @ALTER@ statement is used to manipulate table definitions. It allows to add
 The @<tablename>@ is the table name optionally preceded by the keyspace name.  The @<instruction>@ defines the alteration to perform:
 * @ALTER@: Update the type of a given defined column. Note that the type of the "clustering keys":#createTablepartitionClustering cannot be modified as it induces the on-disk ordering of rows. Columns on which a "secondary index":#createIndexStmt is defined have the same restriction. Other columns are free from those restrictions (no validation of existing data is performed), but it is usually a bad idea to change the type to a non-compatible one, unless no data have been inserted for that column yet, as this could confuse CQL drivers/tools.
 * @ADD@: Adds a new column to the table. The @<identifier>@ for the new column must not conflict with an existing column. Moreover, columns cannot be added to tables defined with the @COMPACT STORAGE@ option.
-* @DROP@: @TODO@ (pending "#3919":https://issues.apache.org/jira/browse/CASSANDRA-3919)
 * @WITH@: Allows to update the options of the table. The "supported @<option>@":#createTableOptions (and syntax) are the same as for the @CREATE TABLE@ statement except that @COMPACT STORAGE@ is not supported. Note that setting any @compaction@ sub-options has the effect of erasing all previous @compaction@ options, so you  need to re-specify all the sub-options if you want to keep them. The same note applies to the set of @compression@ sub-options.
 
+Dropping a column is no yet supported but is on "the roadmap":https://issues.apache.org/jira/browse/CASSANDRA-3919. In the meantime, a declared but unused column has no impact on performance nor uses any storage.
 
 h3(#dropTableStmt). DROP TABLE
 

src/java/org/apache/cassandra/cql3/Cql.g

@@ -448,7 +448,7 @@ alterTableStatement returns [AlterTableStatement expr]
     : K_ALTER K_COLUMNFAMILY cf=columnFamilyName
           ( K_ALTER id=cident K_TYPE v=comparatorType { type = AlterTableStatement.Type.ALTER; }
           | K_ADD   id=cident v=comparatorType        { type = AlterTableStatement.Type.ADD; }
-          | K_DROP  id=cident                         { type = AlterTableStatement.Type.DROP; }
+          // | K_DROP  id=cident                         { type = AlterTableStatement.Type.DROP; }
           | K_WITH  properties[props]                 { type = AlterTableStatement.Type.OPTS; }
           | K_RENAME                                  { type = AlterTableStatement.Type.RENAME; }
                id1=cident K_TO toId1=cident { renames.put(id1, toId1); }