bsd: refine __ntohl() and friends as inline functions

inline functions can be overloaded and are less nasty than macros in other
ways (like evaluating their arguments only once).

Note we can't touch ntohl() itself, since it is defined to be an out-of-line
function by libc.

Signed-off-by: Avi Kivity <avi@cloudius-systems.com>

bsd/sys/sys/param.h

@@ -296,10 +296,10 @@
 
 #define __bswap16_const(_x) (__uint16_t)((_x) << 8 | (_x) >> 8)
 
-#define __htonl(x)  __bswap32_const(x)
-#define __htons(x)  __bswap16_const(x)
-#define __ntohl(x)  __bswap32_const(x)
-#define __ntohs(x)  __bswap16_const(x)
+static inline u_int32_t __htonl(u_int32_t x) { return __bswap32_const(x); }
+static inline u_int16_t __htons(u_int16_t x) { return __bswap16_const(x); }
+static inline u_int32_t __ntohl(u_int32_t x) { return __bswap32_const(x); }
+static inline u_int16_t __ntohs(u_int16_t x) { return __bswap16_const(x); }
 
 /*
  * Basic byte order function prototypes for non-inline functions.