Quash some "may be used uninitialized" warnings.

Quash some "may be used uninitialized" warnings.

/s/mono/mono/mini/interp/interp.c: In function 'interp_entry_from_trampoline':
/s/mono/mono/mini/interp/interp.c:2422:3: warning: 'orig_domain' may be used uninitialized in this function [-Wmaybe-uninitialized]
   mono_threads_detach_coop (orig_domain, &attach_cookie);
   ^
/s/mono/mono/mini/interp/interp.c: In function 'interp_exec_method_full':
/s/mono/mono/mini/interp/interp.c:2695:4: warning: 'locals' may be used uninitialized in this function [-Wmaybe-uninitialized]
    memset (locals, 0, rtm->locals_size);
    ^
/s/mono/mono/mini/method-to-ir.c: In function 'mini_handle_enum_has_flag':
/s/mono/mono/mini/method-to-ir.c:3416:9: warning: 'load' may be used uninitialized in this function [-Wmaybe-uninitialized]
    load = mono_decompose_opcode (cfg, load);
         ^
At least the first two seem to be compiler weakness.