[mod_secdownload] fix compile w/ NSS on FreeBSD

(thx dirk)

nss/alghmac.h might not exist

src/mod_secdownload.c

@@ -25,6 +25,7 @@
 #elif defined(USE_WOLFSSL_CRYPTO)
 #include <wolfssl/wolfcrypt/hmac.h>
 #elif defined(USE_NSS_CRYPTO)
+#if 0 /*(nss/alghmac.h might not be present)*/
 #ifdef NSS_VER_INCLUDE
 #include <nss3/alghmac.h>
 #else
@@ -32,6 +33,7 @@
 #endif
 #endif
 #endif
+#endif
 
 #if defined(USE_OPENSSL_CRYPTO) && OPENSSL_VERSION_NUMBER >= 0x30000000L
 #define HMAC EVP_HMAC