tests: Add char/short/int/AO_double_t and dd_acquire cases to list_atomic

* tests/Makefile.am (list_atomic.c): Iterate over XSIZE/XCTYPE (in
addition to XX); expand XX also as _dd_acquire_read.
* tests/list_atomic.template (XSIZE_list_atomicXX): Define 'val' local
variable only if used (needed for AO_double_t case).