big kernel patch (with lots of changes)

+ implemented thread_destroy, which kills a thread
+ implemented thread_deactivate, which disables a running/ready thread
! fixed linked-list corruption in thread_activate
+ implemented process_remove_thread, which removes a thread from a process
+ implemented creation of popup-threads
+ implemented spurious-IRQ-detection
! correct handling of spurious IRQs
+ implemented registering for IRQs (except the timer-IRQ)
+ implemented IRQ-masking
* the init-process now gets a stack reserved by the kernel
* init now tests port-registering, IRQ-registering and IRQ-popup-threads (it uses the keyboard controller for that)
! the magic number of the ELF-header is now an ubyte-array instead of an uinteger (former implementation had endianess-problems)
* out and inp are now named outb and inb
* moved the syscall-definitions from syscall.bi to syscall_defs.bi
! fixed vmm_unmap_range unmapping more pages than requested
* it's now possible to pass lower_limit and upper_limit to find_free_pages instead of it using hardcoded values
+ implemented vmm_automap
* vmm_kernel_automap now just calls vmm_automap with the current context and the kernels limits
+ assert now prints a stacktrace
* cpu_get_vendor now directly uses the passed zstring pointer instead of a static variable (makes it SMP-safe)
- removed debugging-output from io_man.bas
! fixed kmm's insert_hole crashing when the list of free blocks was (temporarily) empty
* made the check for is_hole in kfree an assert because theres no userspace influence involved
! fixed wrong assert in kfree
! made do_add in kfree a boolean instead of a byte
* mark the cmdline of the multiboot-modules as used in the pmm
! fixed SYSCALL_THREAD_CREATE
* the scheduler now kills threads that couldn't be killed by thread_destroy because they were active
+ implemented an idle-thread which runs in the contect of init, but in ring-0
* cleaned up zstring_len and zstring_instr
! fixed zstring_instr returning an undefined value under certain conditions
+ implemented zstring_cmp and zstring_ncmp (not used yet, but useful for cmdline parsing)
+ added pci- and vgaconsole-modules (only stubs at the moment)