Pipette and "On Preview Widgets" branch. See issue 227

The pipette part is already working quite nice but need to be finished. The widgets part needs more work...

rtengine/klt/error.cc

@@ -0,0 +1,56 @@
+/*********************************************************************
+ * error.c
+ *
+ * Error and warning messages, and system commands.
+ *********************************************************************/
+
+
+/* Standard includes */
+#include <cstdio>
+#include <cstdlib>
+#include <cstdarg>
+
+
+/*********************************************************************
+ * KLTError
+ * 
+ * Prints an error message and dies.
+ * 
+ * INPUTS
+ * exactly like printf
+ */
+
+void KLTError(const char *fmt, ...)
+{
+  va_list args;
+
+  va_start(args, fmt);
+  fprintf(stderr, "KLT Error: ");
+  vfprintf(stderr, fmt, args);
+  fprintf(stderr, "\n");
+  va_end(args);
+  exit(1);
+}
+
+
+/*********************************************************************
+ * KLTWarning
+ * 
+ * Prints a warning message.
+ * 
+ * INPUTS
+ * exactly like printf
+ */
+
+void KLTWarning(const char *fmt, ...)
+{
+  va_list args;
+
+  va_start(args, fmt);
+  fprintf(stderr, "KLT Warning: ");
+  vfprintf(stderr, fmt, args);
+  fprintf(stderr, "\n");
+  fflush(stderr);
+  va_end(args);
+}
+