Fix -Wunused-function warning in ext/pdo_firebird (#15646)

When FB_API_VER equals to 30, for example, on Ubuntu, there is this
warning thrown with certain compiler configurations:

    /php-src/ext/pdo_firebird/pdo_firebird_utils.cpp:21:13: warning:
    ‘void fb_copy_status(const ISC_STATUS*, ISC_STATUS*, size_t)’
    defined but not used [-Wunused-function]
       21 | static void fb_copy_status(const ISC_STATUS* from, ISC_STATUS* to, size_t maxLength)
          |             ^~~~~~~~~~~~~~

Author: petk

ext/pdo_firebird/pdo_firebird_utils.cpp

@@ -18,16 +18,6 @@
 #include <firebird/Interface.h>
 #include <cstring>
 
-static void fb_copy_status(const ISC_STATUS* from, ISC_STATUS* to, size_t maxLength)
-{
-	for(size_t i=0; i < maxLength; ++i) {
-		memcpy(to + i, from + i, sizeof(ISC_STATUS));
-		if (from[i] == isc_arg_end) {
-			break;
-		}
-	}
-}
-
 /* Returns the client version. 0 bytes are minor version, 1 bytes are major version. */
 extern "C" unsigned fb_get_client_version(void)
 {
@@ -51,6 +41,15 @@ extern "C" ISC_DATE fb_encode_date(unsigned year, unsigned month, unsigned day)
 }
 
 #if FB_API_VER >= 40
+static void fb_copy_status(const ISC_STATUS* from, ISC_STATUS* to, size_t maxLength)
+{
+	for(size_t i=0; i < maxLength; ++i) {
+		memcpy(to + i, from + i, sizeof(ISC_STATUS));
+		if (from[i] == isc_arg_end) {
+			break;
+		}
+	}
+}
 
 /* Decodes a time with time zone into its time components. */
 extern "C" ISC_STATUS fb_decode_time_tz(ISC_STATUS* isc_status, const ISC_TIME_TZ* timeTz, unsigned* hours, unsigned* minutes, unsigned* seconds, unsigned* fractions,