Add pg_description table for info on tables, columns, operators, types, and aggregates.  Modify psql with new \dd operator to access description

 for use by recently created macros.

#define StrNCpy(dst,src,len)    \
	(strncpy((dst),(src),(len)),(len > 0) ? *((dst)+(len)-1)='\0' : \
	NULL,(void)(dst))
	     ^^^^^^ - to avoid "value computed is not used" from gcc
	in ma-a-any places (should to fix thouse places instead, but ...
	time)

config.h.in:
/*
 * TBL_FREE_CMD_MEMORY: free memory allocated for an user query inside
 * transaction block after this query is done.
 */
#define TBL_FREE_CMD_MEMORY
- this is default now.

Change a few routine names to ensure <= 16 characters in name
 to fit correctly into pg_proc.