Merge branch 'master' of https://github.com/mallardtheduck/osdev
Fixed memory leak in terminal_write.
Free kernel file handle on close.
Now that we have file I/O, change "zero" call to write debugging output.
Zero memory when loading program.
Added buffer struct for bt_fioctl.
Added stubs for file I/O.
Added BT_FIOCTL implementation.
Removed debugging output from copy_kernelspace.
Prevent possibility of re-mapping already mapped page in vmm_alloc_at.
Set thread PID when loading program to ensure correct page table is in use.