Fixes to address issue: #807

std::unique_ptr<zint_symbol> usage is replaced with:
using unique_zint_symbol = std::unique_ptr<zint_symbol, zint_symbol_deleter>;

This permits the std::move cast used in
void Result::zint(unique_zint_symbol&& z)

{
	_zint = std::shared_ptr(std::move(z));
}

to move the customer deleter usage into the shared pointer too, std::default_delete usage only works for unique_ptr's which is why this change is needed. This prevents ASAN errors that report alloc/dealloc mismatch due to the shared_ptr usage:

(The image is from our internal test pipeline and is of the test that was failing when ASAN is enabled.)