ec fix for search_path with std::filesystem.

closes #287.

include/boost/process/detail/posix/search_path.hpp

@@ -27,7 +27,11 @@ inline boost::process::filesystem::path search_path(
     for (const boost::process::filesystem::path & pp : path)
     {
         auto p = pp / filename;
+#if defined(BOOST_PROCESS_USE_STD_FS)
+        std::error_code ec;
+#else
         boost::system::error_code ec;
+#endif
         bool file = boost::process::filesystem::is_regular_file(p, ec);
         if (!ec && file && ::access(p.c_str(), X_OK) == 0)
             return p;

include/boost/process/detail/windows/search_path.hpp

@@ -61,7 +61,11 @@ inline boost::process::filesystem::path search_path(
         {
             boost::process::filesystem::path pp_ext = p;
             pp_ext += ext;
+#if defined(BOOST_PROCESS_USE_STD_FS)
+            std::error_code ec;
+#else
             boost::system::error_code ec;
+#endif
             bool file = boost::process::filesystem::is_regular_file(pp_ext, ec);
             if (!ec && file &&
                 ::boost::winapi::sh_get_file_info(pp_ext.native().c_str(), 0, 0, 0, ::boost::winapi::SHGFI_EXETYPE_))