Stop using unqualified {GET,PUT}_32BIT.

Those were a reasonable abbreviation when the code almost never had to
deal with little-endian numbers, but they've crept into enough places
now (e.g. the ECC formatting) that I think I'd now prefer that every
use of the integer read/write macros was clearly marked with its
endianness.

So all uses of GET_??BIT and PUT_??BIT are now qualified. The special
versions in x11fwd.c, which used variable endianness because so does
the X11 protocol, are suffixed _X11 to make that clear, and where that
pushed line lengths over 80 characters I've taken the opportunity to
name a local variable to remind me of what that extra parameter
actually does.

unix/uxagentc.c

@@ -73,7 +73,7 @@ static bool agent_try_read(agent_pending_query *conn)
     }
     conn->retlen += ret;
     if (conn->retsize == 4 && conn->retlen == 4) {
-	conn->retsize = toint(GET_32BIT(conn->retbuf) + 4);
+	conn->retsize = toint(GET_32BIT_MSB_FIRST(conn->retbuf) + 4);
 	if (conn->retsize <= 0) {
 	    conn->retbuf = NULL;
 	    conn->retlen = 0;