oops, converted some #ifndef into #if defined...

Convert all #ifdef _KERNEL to #if defined (_KERNEL) || defined(_STANDALONE)
from Bernd Ernesti on source-changes@. This fixes a build breakage
with i386/amd64 bootblocks.

Our qsort() is inappropriate for kernel use because it makes recursive
calls. Replace it with a kheapsort() function in kernel. Pointed out
by tron@.