Fix startup crash when using a locale boost does not like

There are various locale related bugs in various versions of boost,
where exceptions are thrown in boost::filesystem APIs when the
current locale is not to boost's liking. It's not clear what "not
to boost's liking" means in detail, though "en" and "en_US.UTF-8"
are not to its liking.

Fix it by running a test function that's known to throw in such
a case, and resetting LANG and LC_ALL to C if an exception is
thrown. In simplewallet, the locale is queried before that so the
correct translations will still be used.

src/common/util.cpp

@@ -43,6 +43,7 @@ using namespace epee;
 #else 
 #include <sys/utsname.h>
 #endif
+#include <boost/filesystem.hpp>
 
 
 namespace tools
@@ -389,4 +390,22 @@ std::string get_nix_version_display_string()
 #endif
     return std::error_code(code, std::system_category());
   }
+
+  bool sanitize_locale()
+  {
+    // boost::filesystem throws for "invalid" locales, such as en_US.UTF-8, or kjsdkfs,
+    // so reset it here before any calls to it
+    try
+    {
+      boost::filesystem::path p {std::string("test")};
+      p /= std::string("test");
+    }
+    catch (...)
+    {
+      setenv("LC_ALL", "C", 1);
+      setenv("LANG", "C", 1);
+      return true;
+    }
+    return false;
+  }
 }