Build fails with GCC 14

[crashkopf]

With GCC 14 some code that used to cause warning in previous compiler versions now causes errors. From https://gcc.gnu.org/gcc-14/porting_to.html:

The initial ISO C standard and its 1999 revision removed support for many C language features that were widely known as sources of application bugs due to accidental misuse. For backwards compatibility, GCC 13 and earlier diagnosed use of these features as warnings only. Although these warnings have been enabled by default for many releases, experience shows that these warnings are easily ignored, resulting in difficult to diagnose bugs. In GCC 14, these issues are now reported as errors, and no output file is created, providing clearer feedback to programmers that something is wrong.

These changes cause configure and build to fail (see #45 ).

An example build error:

ssh-ecdsa.c:76:18: error: passing argument 1 of ‘DSA_SIG_get0’ from incompatible pointer type [-Wincompatible-pointer-types]
   76 |     DSA_SIG_get0(sig, &r, &s);
      |                  ^~~
      |                  |
      |                  ECDSA_SIG * {aka struct ECDSA_SIG_st *}