BUILD: accept4: move the socketcall declaration outside of accept4()

Gcc 4.2.4 breaks on the syscall declared inside the function, move it
outside and declare it static inline.
diff --git a/include/common/accept4.h b/include/common/accept4.h
index 9c81b80..cc012a2 100644
--- a/include/common/accept4.h
+++ b/include/common/accept4.h
@@ -46,10 +46,10 @@
 /* The syscall is redefined somewhere else */
 extern int accept4(int sockfd, struct sockaddr *addr, socklen_t *addrlen, int flags);
 #elif ACCEPT4_USE_SOCKETCALL
+static inline _syscall2(int, socketcall, int, call, unsigned long *, args);
 static int accept4(int sockfd, struct sockaddr *addr, socklen_t *addrlen, int flags)
 {
 	unsigned long args[4];
-	static _syscall2(int, socketcall, int, call, unsigned long *, args);
 
 	args[0] = (unsigned long)sockfd;
 	args[1] = (unsigned long)addr;