Fix a recently introduces failure of unicode_test. I was trying

to form an argument to logic_error using wstring, which did not work. Now
try to convert wstring into local 8-bit encoding, and use a dummy text
when that fails.


[SVN r25242]

libs/program_options

@@ -1 +1 @@
-Subproject commit ea1ce5aa1f88b097185b3c77f3d1c422c4b78699
+Subproject commit 074c154d18c27f7a80016657d882174ad9b61b60