void xlgscle (nydiv, x, y, npts)  LOGPLT.C  Level 2 
int nydiv  The number of y axis divisions. 
float *x  The vector of x data. 
float *y  The vector of y data. 
int npts  The number of data points in the x and y vectors. 
The selfscaling axis routine, xlgscle(), finds the correct
number of decades so that the logarithmic x axis can accommodate
the data. Labels on log axes are always placed at the decade markings.
Intermediate points are labeled depending on the spacing between divisions.
The y axis is linear.
