crn_decomp: fix: warning: first argument in call to ‘memcpy’ is a pointer to non-trivially copyable type ‘crnd::prefix_coding::decoder_tables’

[illwieckz]

Fix a warning I get when compiling q3map2:

[ 42%] Building CXX object libs/crnrgba/CMakeFiles/crnrgba.dir/crn_rgba.cpp.o
[ 42%] Linking C static library libpicomodel.a
In file included from netradiant/libs/crnrgba/crn_rgba.cpp:31:
netradiant/libs/crnrgba/../crunch/inc/crn_decomp.h:1459:12: warning: first argument in call to 'memcpy'
 is a pointer to non-trivially copyable type 'crnd::prefix_coding::decoder_tables' [-Wnontrivial-memcall]
 1459 |     memcpy(this, &other, sizeof(*this));
      |            ^
netradiant/libs/crnrgba/../crunch/inc/crn_decomp.h:1459:12: note: explicitly cast the pointer to silence
 this warning
 1459 |     memcpy(this, &other, sizeof(*this));
      |            ^
      |            (void*)

[illwieckz]

<perturbed> LGTM https://github.com/DaemonEngine/crunch/pull/84