include: ssp: fix the build with earlier C standards

`inline` isn't always a keyword, so we should be using __ssp_inline
as we do everywhere else in the _FORTIFY_SOURCE support.  Variable
declarations in a loop initializer are also not always supported, so
declare any loop vars in advance.

Reviewed by:	kib (earlier version), markj
Sponsored by:	Klara, Inc.
Sponsored by:	Stormshield
Differential Revision:	https://reviews.freebsd.org/D45976

include/ssp/socket.h

@@ -101,11 +101,12 @@ __ssp_redirect_raw_impl(ssize_t, recvmmsg, recvmmsg,
     const struct timespec *__restrict timeout))
 {
 	const size_t vecsz = __ssp_bos(hdrvec);
+	size_t i;
 
 	if (vecsz != (size_t)-1 && vecsz / sizeof(*hdrvec) < vlen)
 		__chk_fail();
 
-	for (size_t i = 0; i < vlen; i++) {
+	for (i = 0; i < vlen; i++) {
 		__ssp_check_msghdr(&hdrvec[i].msg_hdr);
 	}
 

include/ssp/ssp.h

@@ -89,7 +89,7 @@ __ssp_redirect_raw_impl(rtype, fun, symbol, args) { \
 
 #include <machine/_stdint.h>
 
-static inline int
+__ssp_inline int
 __ssp_overlap(const void *leftp, const void *rightp, __size_t sz)
 {
 	__uintptr_t left = (__uintptr_t)leftp;
@@ -112,11 +112,12 @@ __ssp_inline void
 __ssp_check_iovec(const struct iovec *iov, int iovcnt)
 {
 	const size_t iovsz = __ssp_bos(iov);
+	int i;
 
 	if (iovsz != (size_t)-1 && iovsz / sizeof(*iov) < (size_t)iovcnt)
 		__chk_fail();
 
-	for (int i = 0; i < iovcnt; i++) {
+	for (i = 0; i < iovcnt; i++) {
 		if (__ssp_bos(iov[i].iov_base) < iov[i].iov_len)
 			__chk_fail();
 	}