boost: fix "locale::facet::_S_create_c_locale name not valid" error

One would assume that the boost maintainers would have been able to apply this
two line change within the last 10 months or so, but apparently not.

svn path=/nixpkgs/trunk/; revision=27864

pkgs/development/libraries/boost/boost_filesystem.patch

@@ -0,0 +1,24 @@
+diff -ubr boost_1_47_0/libs/filesystem/v2/src/v2_path.cpp boost_1_47_0-patched/libs/filesystem/v2/src/v2_path.cpp
+--- boost_1_47_0/libs/filesystem/v2/src/v2_path.cpp	2011-01-11 22:39:33.000000000 +0100
++++ boost_1_47_0-patched/libs/filesystem/v2/src/v2_path.cpp	2011-07-21 01:06:26.000000000 +0200
+@@ -45,7 +45,7 @@
+   {
+ #if !defined(macintosh) && !defined(__APPLE__) && !defined(__APPLE_CC__) 
+     // ISO C calls this "the locale-specific native environment":
+-    static std::locale lc("");
++    static std::locale lc;
+ #else  // Mac OS
+     // "All BSD system functions expect their string parameters to be in UTF-8 encoding
+     // and nothing else."
+diff -ubr boost_1_47_0/libs/filesystem/v3/src/path.cpp boost_1_47_0-patched/libs/filesystem/v3/src/path.cpp
+--- boost_1_47_0/libs/filesystem/v3/src/path.cpp	2011-07-05 16:49:42.000000000 +0200
++++ boost_1_47_0-patched/libs/filesystem/v3/src/path.cpp	2011-07-21 01:06:26.000000000 +0200
+@@ -767,7 +767,7 @@
+     // or LANG are wrong, for example), so dynamic initialization is used to ensure
+     // that exceptions can be caught.
+ 
+-    return std::locale("");
++    return std::locale();
+ 
+ #   endif
+   }

pkgs/development/libraries/boost/default.nix

@@ -48,6 +48,9 @@ stdenv.mkDerivation {
     sha256 = "815a5d9faac4dbd523fbcf3fe1065e443c0bbf43427c44aa423422c6ec4c2e31";
   };
 
+  # See <http://svn.boost.org/trac/boost/ticket/4688>.
+  patches = [ ./boost_filesystem.patch ];
+
   enableParallelBuilding = true;
 
   buildInputs = [icu expat zlib bzip2 python];