Add -Wstrict-prototypes option to --strict-warnings

[extended tests]
Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NRichard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6542)

Configure

@@ -125,6 +125,7 @@ my $gcc_devteam_warn = "-DDEBUG_UNUSED"
         . " -Wswitch"
         . " -Wsign-compare"
         . " -Wmissing-prototypes"
+        . " -Wstrict-prototypes"
         . " -Wshadow"
         . " -Wformat"
         . " -Wtype-limits"

crypto/ct/ct_log.c

@@ -46,7 +46,7 @@ typedef struct ctlog_store_load_ctx_st {
  * Creates an empty context for loading a CT log store.
  * It should be populated before use.
  */
-static CTLOG_STORE_LOAD_CTX *ctlog_store_load_ctx_new();
+static CTLOG_STORE_LOAD_CTX *ctlog_store_load_ctx_new(void);
 
 /*
  * Deletes a CT log store load context.

crypto/ec/curve25519.c

@@ -150,7 +150,7 @@ void x25519_fe51_mul121666(fe51 h, fe51 f);
 
 typedef uint64_t fe64[4];
 
-int x25519_fe64_eligible();
+int x25519_fe64_eligible(void);
 
 /*
  * There are no reference C implementations for this radix.

test/testutil/driver.c

@@ -26,7 +26,7 @@
  */
 typedef struct test_info {
     const char *test_case_name;
-    int (*test_fn) ();
+    int (*test_fn) (void);
     int (*param_test_fn)(int idx);
     int num;