Fix Oracle producer

generating an unnecessary / at the end in case there are no triggers
Factor out quote option handling
Fix quoting in Producer::MySQL
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.
Escape the closing quote character when quoting indentifiers
Fix handling of quoted names in Parser::SQLite
Fix handling of quoted names in Parser::MySQL
Fix handling of quoted names in Parser::PostgreSQL
Test table and field names with quote characters in them
Fix handling of quoted literals in Parser::SQLServer
Escape the quote charcter when quoting identifiers in Producer::Oracle
Fix handling of quoted names in Parser::Oracle
Fix handling of quoted strings in Parser::Oracle
Fix parsing of DROP statements in Parser::Oracle

The grammar is still severely lacking, but at least now it passes
t/60roundtrip.t with a trivial table (no auto-increment or foreign
keys).
Fix escaping/parsing of single-quoted strings in SQLite

Also fix parsing of decimal numbers.
Fix decimal and single-quoted values in Parser::PostgreSQL
Escape single quotes in string default values
Escape single quotes in string default values for Oracle
Fix handling of escaped quote characters and numeric literals in MySQL
Quote table names in 'SHOW CREATE TABLE' in Parser::DBI::MySQL