[PATCH] secur32: Fix compile error on older gnutls.

[Marvin]

Hi,

While running your changed tests on Windows, I think I found new failures.
Being a bot and all I'm not very good at pattern recognition, so I might be
wrong, but could you please double-check?

Full results can be found at:
https://testbot.winehq.org/JobDetails.pl?Key=47301

Your paranoid android.


=== debian9 (build log) ===

../../../wine/dlls/secur32/schannel_gnutls.c:57:12: error: static declaration of ‘gnutls_privkey_import_rsa_raw’ follows non-static declaration
Makefile:349: recipe for target 'schannel_gnutls.o' failed
Makefile:8660: recipe for target 'dlls/secur32' failed
Task: The win32 build failed

=== debian9 (build log) ===

../../../wine/dlls/secur32/schannel_gnutls.c:57:12: error: static declaration of ‘gnutls_privkey_import_rsa_raw’ follows non-static declaration
Makefile:342: recipe for target 'schannel_gnutls.o' failed
Makefile:8383: recipe for target 'dlls/secur32' failed
Task: The wow64 build failed