1366x768 resolution missing

I use ArchLinux with QEMU 1.2.0.
I found that 1366x768 resolution is missing, even if I use -vga std or -vga vmware.
I think that it is necessary to patch it into the source.
Also, why not add a command-line option to specify custom resolutions without patching the source? (I know that VirtualBox has a hidden option to add any resolution.)