Usage

- Parameters:
	1. FD to read from
	2. Pointer to char* where line will be stored in.
- Allocation is done by GNL for line, so this should be freed by the user.
- Return values:
	 1: line read.
	 0: End of File read.
	-1: Error (read or malloc)
- Each call will return the next line of the FD.
- If FD changes files between calls, behavior is undefined.

Mandatory part

- Line will be malloced inside GNL, and should be freed by the user.
- Works for single FD only
- No leaks if you stop calling GNL before EOF

Bonus part

- Works for multiple FDs.
- Will have unfreed memory that was allocated if GNL calls stop before EOF.
- Uses linked list to handle multiple FDs, one list element per FD.