WL#3172: SHOW CREATE TABLE: Add character set/collation info

Affects: Server-7.1   —   Status: Un-Assigned   —   Priority: Medium

A request from Support:
Add the names of the default character set and the
default collation to SHOW CREATE TABLE. Currently,
for this statement:
  col1 CHAR(5), 
  col2 CHAR(5) CHARACTER SET latin1 COLLATE latin1_swedish_ci);
the SHOW CREATE TABLE statement shows the character
set and collation information for col2 because it's
explicitly specified. But it does not show the same
information for col1, since those values default.
But users may not know what their default character
set/collation values are, so this is useful information
to provide.

While we're at it, we could also change other things ...

The clause order now is COLLATE x NOT NULL DEFAULT x.
The clause order should be DEFAULT x NOT NULL COLLATE x, as in standard SQL.

Numeric default literals are quoted, for example DEFAULT '5'.
They should not be quoted.