GPGME_ENCRYPT_NO_ENCRYPT_TO not available

[immerda]

When I install the gem GPGME_ENCRYPT_NO_ENCRYPT_TO is not available, even though I have a recent enough gpgme version, which should report it.

Additionally the flag is not exposed in the high-level api. It would be nice if I could set it as an option.

If you have any pointers why the symbol is not exposed at all, I could provide a patch for the second problem...

[djberg96]

@ueno Can confirm this. It looks like that constant and related constants are actually within an enum so the #ifdef check is failing. Might be easier to add have_const checks in the extconf.rb file and use that macro check instead.