WL#936: CLOB and NCLOB

We should allow the CLOB (Character Large OBject) 
and NCLOB (National Characer Large OBject) data 
types. 
 
CLOB is like VARCHAR, only bigger. 
 
NCLOB is like NATIONAL CHAR VARYING, only bigger. 
 
Example: 
 
CREATE TABLE t (s1 CLOB (1000000)) 
INSERT INTO t VALUES ('The rain in Spain') 
 
The size may be abbreviated using multipliers K,M or G:
'K' for kilobytes 'M' for megabyte or 'G' for gigabyte. 

For example:  

CREATE TABLE t (s1 CLOB (1K)) /* size = 1 kilobyte */  
CREATE TABLE t (s1 CLOB (1M)) /* size = 1 megabyte */  
CREATE TABLE t (s1 CLOB (1G)) /* size = 1 gigabyte */  

Space characters may appear between number and multiplier:

CREATE TABLE t (s1 CLOB (1 K))
CREATE TABLE t (s1 CLOB (1 M))
CREATE TABLE t (s1 CLOB (1 G))

Optionally, length units can be specified, either CHARACTERS or BYTES:

CREATE TABLE t (s1 CLOB (1K CHARACTERS))
CREATE TABLE t (s1 CLOB (1K BYTES))