Fix subkey check to cope with ECC subkeys

ECC subkeys are type 18 and we were only excluding type 19+, causing
false positives on the weak subkey test.

debian/changelog

@@ -9,6 +9,7 @@ debian-keyring (2018.05.xx) UNRELEASED; urgency=medium
   [ Jonathan McDowell ]
   * Temporarily remove 0x021B361B6B031B00 (Julian Andres Klode) due to
     subkey loss
+  * Fix subkey check to cope with ECC subkeys
 
  -- Gunnar Wolf <gwolf@debian.org>  Wed, 30 May 2018 10:05:20 -0500
 

t/at-least-2048.t

@@ -9,7 +9,7 @@ find_too_short () {
 		| awk -F: -v keyring=$1 \
 		'BEGIN { ok = 1 } \
 		/^pub/ { fpr = $5 ; if ($3 < 2048) { print keyring ":\t0x" $5 " is smaller than 2048 bits"; ok = 0 } } \
-		/^sub/ { if ($2 != "r" && $2 != "e" && $3 < 2048 && $4 < 19) { print keyring ":\t0x" fpr " has subkey smaller than 2048 bits"; ok = 0 } } \
+		/^sub/ { if ($2 != "r" && $2 != "e" && $3 < 2048 && $4 < 18) { print keyring ":\t0x" fpr " has subkey smaller than 2048 bits"; ok = 0 } } \
 		END { if (!ok) { exit 1 } }'
 }