Builtin specificities :
	- CD
		- OLDPWD and PWD are only updated if the were declared before executing cd.
		- CDPATH : matching folder in the working directory have the priority over
			matching folders in CDPATH variable.
	- EXIT
		- exit command will ALWAYS exit, even if incorrect argument are given (exit status
			will be set accordingly).

Handled
	- && and || sign with parenthesis interpreted as subshell execution.
	- wildcards (*)

Not handled
	- cd with '-' argument
	- shlvl
	- export with '+=' sign.

ISSUE
	- Ctrl-\ in interactive mode updates error status to 130
		(because readline() keeps setting errno to
		something when catching the signal)
	- if a prompt use here_doc (<<) within parenthesis and outside parenthesis at the same time, the order of different calls to here_doc will not follow left to right.
		- the final order depends of how the parenthesis are nested within each other