math: move feature tests outside of DEFTYPE WORD

When DEFTYPE WORD contains the feature tests for
QUAVIVER/BIGNUM-ELISION, ECL and Clasp seem to have trouble
understanding the type declarations in Dragonbox.

code/math/implementation.lisp

@@ -1,18 +1,20 @@
 (in-package #:quaviver/math)
 
+#+quaviver/bignum-elision
 (deftype word (arithmetic-size &optional (count 1))
-   #+quaviver/bignum-elision
-   (ecase arithmetic-size
-     (32 (case count
-           (1 `(unsigned-byte 32))
-           (2 `(unsigned-byte 64))
-           (otherwise `(simple-array (unsigned-byte 64) (,(ceiling count 2))))))
-     (64 (if (eql count 1)
-             `(unsigned-byte 64)
-             `(simple-array (unsigned-byte 64) (,count))))
-     (128 `(simple-array (unsigned-byte 64) (,(ash count 1)))))
-   #-quaviver/bignum-elision
-   `(unsigned-byte ,(* arithmetic-size count)))
+  (ecase arithmetic-size
+    (32 (case count
+          (1 `(unsigned-byte 32))
+          (2 `(unsigned-byte 64))
+          (otherwise `(simple-array (unsigned-byte 64) (,(ceiling count 2))))))
+    (64 (if (eql count 1)
+            `(unsigned-byte 64)
+            `(simple-array (unsigned-byte 64) (,count))))
+    (128 `(simple-array (unsigned-byte 64) (,(ash count 1))))))
+
+#-quaviver/bignum-elision
+(deftype word (arithmetic-size &optional (count 1))
+  `(unsigned-byte ,(* arithmetic-size count)))
 
 ;;; Bignum elision
 ;;;