Allow 8192 bit RSA keys to be selected when generating keys interactively

with --full-generate-key and --enable-large-rsa

Based on https://lists.gnupg.org/pipermail/gnupg-devel/2015-February/029466.html

--- g10/keygen.c.orig	2018-08-14 13:22:40 UTC

+++ g10/keygen.c

@@ -2116,7 +2116,7 @@ get_keysize_range (int algo, unsigned in

     default:

       *min = opt.compliance == CO_DE_VS ? 2048: 1024;

-      *max = 4096;

+      *max = (opt.flags.large_rsa ? 8192 : 4096);

       def = 2048;

       break;

     }