various inefficient median routines

[teuben]

median.c is only defining a pointer based index sorting, (sortptr) which can be very slow.
turns out that median() is quite fast if a pre-sorted array is used.
this median -> pmedian (old one) and smedian( new one, assumes arrays were pre-sorted, e.g. with qsort()

programs which need to be refactored for this:
tabhist
tabstat
ccdstat (speedup is quite large for median=t)

and the library modules
median
moment

need some patches.

[teuben]

listed routines have been committed. ready to close item?