add support for CREATE TEMPORARY TABLE

[leiysky]

What problem does this PR solve?

Add support for CREATE TEMPORARY TABLE #408

What is changed and how it works?

MySQL syntax:

create_table_stmt:
          CREATE opt_temporary TABLE_SYM opt_if_not_exists table_ident
          '(' table_element_list ')' opt_create_table_options_etc
        | CREATE opt_temporary TABLE_SYM opt_if_not_exists table_ident
          opt_create_table_options_etc

Check List

Tests

• Unit test

[codecov]

Codecov Report

Merging #438 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #438      +/-   ##
==========================================
+ Coverage   70.84%   70.85%   +0.01%     
==========================================
  Files          32       32              
  Lines        7501     7504       +3     
==========================================
+ Hits         5314     5317       +3     
  Misses       1674     1674              
  Partials      513      513

Impacted Files	Coverage Δ
parser.go	70.58% <ø> (ø)	⬆️
ast/ddl.go	78.5% <100%> (+0.04%)	⬆️

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[tangenta]

@leiysky TiDB does not support TEMPORARY tables. Would you please add a warning in the parser for both CreateTableStmt and DropTableStmt?

[leiysky]

@tangenta PTAL

[tangenta]

LGTM

[tangenta]

@leoppro PTAL

[zier-one]

LGTM