Expand the DYE_MACRO_UUID macro

An extra level of macro expansion is required, as the ## preprocessing
operator does not perform expansion prior to concatenation, resulting
symbols like `dye_scope_guard_DYE_MACRO_UUID` instead of symbols like
`dye_scope_guard_4029617a_ebbc_11e3_a02d_080027989a56`.

Of course, the UUID needed hyphens replaced (with underscores in this
case) for concatenated symbols to be valid C/C++ symbols.