Improve the implement to generate expressions in bytecode generator

Differentiate the rules the generate single or multiple values and
introduce a specific function expr_toanyreg to store expression without
explicit register destination.
Add some more generic tests
Modify behaviour on -b flag to print only the bytecode
Modify output testing script to print the test results directly
Implement automated tests for the bytecode output
Improve one of the logical values test
Modify .gitignore to avoid showing files generated by test script
Modify test suite to write output bytecode in log directory
Improve logical test from the test suite
Add expect bytecode files for the test suite

The expect files cover some know differences with LuaJIT2 in the
generated bytecode.
Rename test suite scripts
Fix expect test for logical-tests-4b.lua
Improve UCLO code generation by using scope-specific informations
Update and expand README file