kernel: add free page system call

kernel: reserve first 16 pages of a service to make accidental Null pointer resolutions thorw an exception

kernel: fix compiler warning about invalid pointer conversion

kernel: avoid crashes (double faults) by blocking interrupts during execution

use ld-level allocation of allocation data object for all programs and kernel

hlib: declare allocation data in linker script

hid: refactor io parameters for input tag

add mouse service to manage mouse position

add fork system call

kernel await / fire event: add code to wait for specific event

usb xhci: send configure endpoint command to set up endpoints

xhci refactoring: sperate out all xhci-related code to its own directory

make printf function available for not-main userland files

xhci: refactor and seperate out commands

fix issue #3: crash when running an unknown program

xhci: clean up slot initialization

fix weird problems with getPhysicalAddress system call

fix issue with printing where the first message would not get printed

create async xhci command function using events

trigger interrupts from xhci controller

fix problem where page fault happens because not the whole string is mapped in a insertString system call

refactor syscall.c

add sleep function to PIT driver

receive xhci events

fix issue #1: ELF files not loaded correctly

add system call to retrieve the physical location of a virutal address

print basic XHCI information

add lspci user programm

move 'gets'-functionality to ioManager to simplify the shell source code

add await syscall