Interactive non-linear curve fitting tools.

This package is similar to the original one found in iraf$pkg/xtools/icfit/,
but with extensive internal modifications to allow overlaying on top of NLFIT
package instead of CURFIT. Major modifications are: 

- allowed function types: bbody, powerlaw, composite, Gaussians.
- graphing of individual function components in the composite and Gaussians 
  cases.
- graphs data and guessed function before fitting; waits explicitly for 'f' key.
- new cursor keystrokes: b (baseline), p (Gaussian positions), z (print cursor
  coordinates).
- new colon commands: coef, fix, vary, ngauss, rms, pcomp.
- new meaning to 'errors' colon command.
- 'order' colon command eliminated.
- 'show' colon command upgraded to show coefficient values, errors and status.
- 'vshow' colon command modified to print xdata, ydata, yfunction and residue 
  for each datum.
- new cursor help file
- no more choice between single and double precision versions.
- procedure name prefixes were changed to nc_ instead of ic_. This is 
  acomplished with the new include file "names.h"
							<Busko 3/10/89>

