[clang][Interp][NFC] Use a smaller default size for IntegralAP

Since we later possibly initialize the value by using operator-new,
we need the default value to _not_ allocate memory.

Author: tbaederr

clang/lib/AST/Interp/IntegralAP.h

@@ -61,7 +61,7 @@ template <bool Signed> class IntegralAP final {
 
   IntegralAP(APInt V) : V(V) {}
   /// Arbitrary value for uninitialized variables.
-  IntegralAP() : IntegralAP(-1, 1024) {}
+  IntegralAP() : IntegralAP(-1, 3) {}
 
   IntegralAP operator-() const { return IntegralAP(-V); }
   IntegralAP operator-(const IntegralAP &Other) const {