Fix line number in parser for while statements
Fix debug line information for end-of-loop instruction

Does the same of luajit and set the line information for the closing loop
instruction to the first line of the loop.
Add explicit method to set bytecode current instruction's line number
Add debug line information for expressions
Better code factorization in for block and chunk parser
Track the line number of "end" keyword for loops
Add line information for statement blocks in parser
Improve line number information in bytecode for statement blocks

Write end-of-block line number on block_leave or close_proto.
Fix bug related to a mispelled variable in bcread
Fix phantom space character in bytecode generator