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.

windows/winpgntc.c

@@ -109,7 +109,7 @@ agent_pending_query *agent_query(
      */
     id = SendMessage(hwnd, WM_COPYDATA, (WPARAM) NULL, (LPARAM) &cds);
     if (id > 0) {
-	retlen = 4 + GET_32BIT(p);
+	retlen = 4 + GET_32BIT_MSB_FIRST(p);
 	ret = snewn(retlen, unsigned char);
 	if (ret) {
 	    memcpy(ret, p, retlen);