Combining ~T and ~<~:;~>

[Eric Timmons]

I've been using ECL to compile SBCL on aarch64, but I can't do it
without patching the sources. There is a warning triggered during the
build (only on aarch64) with a format string that contains:

~<~%~9T~:;~/sb-impl:print-type/:~>

ECL chokes on this due to the ~T in the ~:; clause. Why is that not
allowed? It seems like a reasonable thing to do at first glance.

-Eric