Clean up option parsing and identifier quoting in Producer::PostgreSQL

Remove the unused quote_field_names and table_name options and use the
factored-out quote option parsing function.
Clean up option parsing and fix identifier quoting in Producer::MySQL
Fix handling of quoted identifiers and strings in Parser::SQLite
Fix handling of quoted identifiers and strings in Parser::MySQL
Fix handling of quoted identifiers and strings in Parser::PostgreSQL
Fix handling of quoted identifiers and strings in Parser::SQLServer
Fix handling of quoted identifiers and strings in Parser::Oracle
Escape the closing quote character when quoting indentifiers
Test table and field names with quote characters in them
Escape quotes in string values in producers
Test round-tripping default values with quotes and backslashes
Test round-tripping decimal default values
Test quotes in field comments
Quote table names in 'SHOW CREATE TABLE' in Parser::DBI::MySQL
Add Changes entry for quoting fixes
Handle ALTER TABLE ... ADD CONSTRAINT in Parser::Oracle
Add support for triggers in Parser::Oracle
Narrow the scope of Oracle roundtrip TODO

The parser can now understand the producer output, but doesn't turn the
triggers it generates back into is_auto_increment and timestamp fields.