Modifying exception throwing in Sync::Digest

Now there are more diagnostic information attached to each exception
diff --git a/wscript b/wscript
index 7f4f1b3..443bf49 100644
--- a/wscript
+++ b/wscript
@@ -4,6 +4,7 @@
 APPNAME='sync'
 
 def options(opt):
+    opt.add_option('--no-debug',action='store_true',default=False,dest='no_debug',help='''Make an optimized build of the library (remove debugging code)''')
     opt.load('compiler_c')
     opt.load('compiler_cxx')
     opt.load('boost')
@@ -25,7 +26,8 @@
     conf.check_tinyxml (path=conf.options.ccnx_dir)
 
     conf.define ('STANDALONE', 1)
-    # conf.define ('DIGEST_BASE64', 1) # base64 is not working and probably will not work at all
+    if not conf.options.no_debug:
+        conf.define ('_DEBUG', 1)
 	
 def build (bld):
     bld.shlib (target=APPNAME,