Fix get_database_size on Windows

Replace all calls to epee::file_io::get_file_size with
boost::filesystem::file_size in order to avoid lossy conversions from
paths to strings, which tend to break filename resolution. This commit
fixes a bug on Windows where the get_info RPC call reported a zero
database size because BlockchainLMBD::get_database_size returned zero.

contrib/epee/src/file_io_utils.cpp

@@ -149,40 +149,5 @@ namespace file_io_utils
 		}
 #endif
 	}
-
-
-	bool get_file_size(const std::string& path_to_file, uint64_t &size)
-	{
-#ifdef _WIN32
-                std::wstring wide_path;
-                try { wide_path = string_tools::utf8_to_utf16(path_to_file); } catch (...) { return false; }
-                HANDLE file_handle = CreateFileW(wide_path.c_str(), GENERIC_READ, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
-                if (file_handle == INVALID_HANDLE_VALUE)
-                    return false;
-                LARGE_INTEGER file_size;
-                BOOL result = GetFileSizeEx(file_handle, &file_size);
-                CloseHandle(file_handle);
-                if (result) {
-                    size = file_size.QuadPart;
-                }
-                return size;
-#else
-		try
-		{
-			std::ifstream fstream;
-			fstream.exceptions(std::ifstream::failbit | std::ifstream::badbit);
-			fstream.open(path_to_file, std::ios_base::binary | std::ios_base::in | std::ios::ate);
-			size = fstream.tellg();
-			fstream.close();
-			return true;
-		}
-
-		catch(...)
-		{
-			return false;
-		}
-#endif
-	}
-
 }
 }