Added stub for sys__fork.
Added a pid_t field to struct proc which is used to store the process id of the process.
Refactored some code by moving it from proc_syscalls.c to proc.c.
Added functions to get an unused pid, and proc_create now assigns process ids to processes. The kernel process has no current process (curproc) when it’s being created, so its parent process id is the same as its own process id. Implemented create_map_for_process() which creates a new pid_exitcode_map for a process with it’s process id and it’s parent’s process id. Implemented add_map_to_map_array() which adds a pid_exitcode_map to the pid_exitcode_map_array. Implemented add_exitcode_for_pid_to_map() which adds an exitcode to the exitcode_pid_map specified by the pid_t passed in. Implemented get_map_for_pid() which returns the pid_exitcode_map with the given pid. Implemented get_exitcode_for_pid() which returns an exitcode of a process with the given pid.
Started implementing sys__fork(). Moved a bunch of code to proc.c.