all IO-related things:
* get back verbose IO messages about fread-vs-directIO
* enable imagemagick-style format flagging on filenames ("PNM:-"),
thereby obviating "unu save -f pnm" steps in pipes to standard out
* to expand multiple-format handling: in nrrdRead(), generalize
_nrrdOneLine to some more generation _nrrdReadStart, which puts some
portion of the read file into nio.  The various formats' readTest()
methods need to look at that content, possibly reading in more of the
file, in order to see if they will accept the file one of their own.
The nrrdFormatAll array (or whatever its been renamed to) may need some
care in how the formats are ordered, so that if a given filename could
belong to more than one format (for writing) or if the initial content
of a filename could be in more than one format (for reading), then
perhaps the ordering of nrrdFormatAll would impose some preferential
ordering on the formats.
* generalize I/O so that magic needn't be on line by itself
* support Analyze/NIFTI format (relies on better buffering, above)
* support DICOM, using as much of something like DCMTK as needed
* clarify and document all IO stuff
* debug and scrutinize current implementation of all "nhdr" related behavior
* support TIFF format
* support FITS format
* support VFF format
* other encodings- base 85

nrrd: look into Pade approximations for windowed sinc() kernels

add more internal types to stuff in arith.c for these:
new nrrdBinaryOps: bit-wise and (&), or (|), xor (^)
new nrrdUnaryOps: bit-wise not (^)

call fflush(file) before airDioTest() ?

sampleUnits map to histogram axis with all things histo

nrrd: speed up nrrdCCFind

nrrd: figure out some framework for lazy evaluation stuff

unu heq should not DIE if min==max, it should just be a no-op.
unu heq -s 2 shouldn't DIE if there are only 2 bins with any hits

follow heq with clamp so that there's no value wrap-around
(noticed this with unu heq -a -1)

test working with nout==nin
nrrdContentSet
nrrdConvert
nrrdQuantize
nrrdUnquantize

test regular and irregular colormaps with only 2 points, purify unu
{lut, rmap, imap} with scalar and nonscalar, type same and different
than map type.

check resampler getting info with NULL kernel on each axis
(bug that Joe and I had with qbert when no resmapling was needed)

write a select() function to replace qsort() in median calculation

be sure to test all non-boolean state/default variables

add one-line descriptions to function declarations in nrrd.h

see if the use of airSinglePrintf in accessors.c, with %.8g or whatever,
is really the right thing to do in the most general case

see which of the nrrdDef* variables are actually used, but this
is harder than just grepping through files for the nrrdDef* name;
you have to see where the variable is used that initially is set
to the nrrdDef* value.

Bricking!

split?  (reverse of join)

make nrrdDescribe() a little prettier

create textual representation of resampling parameters

revisit resampler, one last time
go through all functions to:
- determine when nin can == nout
- pass "content" correctly
- make sure content adjustment agrees with unrrdu

try setting NRRD_DIM_MAX to 2 or 3 and doing lots of unrrdu stuff

verify behavior WRT min/max/center:
  reorder.c, measr.c, histogram.c, map.c, arith.c, filt.c
verify behavior WRT blocks:
  all
verify that all axis and nrrd fields are accounted for
  all functions making a "nout" from a "nin"

where does nrrd check to see it got a reasonable axis size,
how and when does nrrd set the default size to 0
