fix ImageJ viewer NullPointerException on Snap button press

ImagePlus.getProcessor() will return null if the ImagePlus
instance has no ImageProcessor nor AWT Image.  This can occur in
EPICS_AD_Viewer.makeImageCopy(), so it needs to handle this case to
avoid a NullPointerException.

One way to reproduce this problem is to start the areaDetector
Simulator, but don't acquire any frames.  Then in the ImageJ viewer,
connect to the AD simulator Image1 plug-in (i.e. 13SIM1:image1:),
press "Start", and then press "Snap".  This will produce a
NullPointerException.  There are likely other ways to reproduce this
problem probably involving closing the image window and pressing the
"Snap" button.
Add xml2 to PROD_SYS_LIBS on solaris and Darwin
Add xml2 to LIB_SYS_LIBS on Linux, solaris and Darwin
Merge pull request #37 from jlmuir/fix-imagej-viewer-npe

fix ImageJ viewer NullPointerException on Snap button press
Changed release date
Fixed release date for R2-1
New file
Conditionally build based on EPICS_LIBCOM_ONLY flag
Add EPICS_LIBCOM_ONLY flag which disables PVAttribute and functAttribute
Support EPICS_LIBCOM_ONLY flag; fixed for WIN32
Fixes for WIN32
Install all .h files for use by external programs
Install simDetector.h for use by other applications
New file
Removed class definition to external simDetector.h file; define reasonable defaults for some parameters
Add simDetectorNoIOC; conditionally build simDetectorIOC
New file
New version