Add some error checking to inputs to xyxymatch

[jdavies-st]

The python wrapper script for xyxymatch

stsci.stimage/stsci/stimage/__init__.py

Line 41 in 222d47b

def xyxymatch(input,

just passes along the inputs to the C code. If they are the wrong numpy shape or numpy type, one gets a segfault. It would be nice to add some guard rails to this, i.e. verify the 2 required input numpy shapes are correct.