Added a utility function to 'print' a text description of errors

in error_numbers.h.  In the future, when adding a new error number
to this file, please update boincerror() in util.C to contain a
short text description of the error.

svn path=/trunk/boinc/; revision=5997

checkin_notes

@@ -5958,4 +5958,5 @@ Bruce 1 May 2005
     lib/
         error_numbers.h
         util.C
+        util.h
 

lib/util.h

@@ -127,4 +127,9 @@ extern int boinc_calling_thread_cpu_time(double&);
 //
 extern void mysql_timestamp(double, char*);
 
+// returns short text description of error corresponding to
+// int errornumber from error_numbers.h
+//
+extern const char* boincerror(int which_error);
+
 #endif