Fix + clean up the old heap stress test
Update Lua from 5.2.1 to 5.2.3
Solve a rare crash (task.c) and some minor stuff
Add kheap_is_valid, HEAP_SERIAL_DEBUG and change an assert() to if()
ata.c: Minor logic change in sectors_to_read
Undo previous panic change, with a comment explaining why
Move the KERNEL_STACK_SIZE define to header file + add a TODO item
Rename _cur_ino to cur_block
A few minor things.

* Update CHECKLIST with pipes now working (since last year)
* Use initrd for / (this changes now and then while I work)
* Using mutexes where task switching is disabled is probably very bad
Fix Newlib compile warning
Use unsigned int instead of uint32 in ls