include/compat: define aligned_free() as a function not a macro

include/compat: define aligned_free() as a function not a macro

so it does not get substituted by the preprocessor unconditionally.
this change helps to address the compiling failure when using boost
1.79 using MinGW, like:

../build.deps/mingw/boost/include/boost/align/aligned_allocator.hpp: In member function 'void boost::alignment::aligned_allocator<T, Alignment>::deallocate(boost::alignment::aligned_allocator<T, Alignment>::pointer, boost::alignment::aligned_allocator<T, Alignment>::size_type)':
../src/include/compat.h:352:27: error: '_aligned_free' is not a member of 'boost::alignment'; did you mean 'aligned_free'?
  352 | #define aligned_free(ptr) _aligned_free(ptr)
      |                           ^~~~~~~~~~~~~

Signed-off-by: Kefu Chai <tchaikov@gmail.com>