Port the fix for large unsigned integers.

As @haarg demonstrated in tobyink/p5-type-tiny-xs#9,
previous "fix" breaks for large unsigned integers.

@haarg also pointed out that macro ended with "p" such as SvIOKp should be avoided,
since that check the flag for ["non-public integer values"][1], and the one without p ("SvIOK")
checks the flag for ["public integer values"][2]

[1]: https://perl5.git.perl.org/perl.git/blob/HEAD:/sv.h#l369
[2]: https://perl5.git.perl.org/perl.git/blob/HEAD:/sv.h#l364

t/101_issues/Int.t

@@ -35,4 +35,11 @@ subtest "Int from integer literal: my \$num = 3", sub {
     ok $Int->check($num), "\$num is still Int";
 };
 
+subtest "MAXUINT", sub {
+    my $maxuint = ~0;
+    ok $Int->check( $maxuint ), 'yes MAXUINT';
+    my $as_string = sprintf '%f', $maxuint;
+    ok $Int->check( $maxuint ), 'yes MAXUINT after use as float';
+};
+
 done_testing;

xs-src/MouseTypeConstraints.xs

@@ -168,16 +168,16 @@ S_nv_is_integer(pTHX_ NV const nv) {
 int
 mouse_tc_Int(pTHX_ SV* const data PERL_UNUSED_DECL, SV* const sv) {
     assert(sv);
-    if(SvPOKp(sv)){
+    if(SvPOK(sv)){
         int const num_type = grok_number(SvPVX(sv), SvCUR(sv), NULL);
         return num_type && !(num_type & IS_NUMBER_NOT_INT);
     }
-    else if(SvNOKp(sv)) {
-        return S_nv_is_integer(aTHX_ SvNVX(sv));
-    }
-    else if(SvIOKp(sv)){
+    else if(SvIOK(sv)){
         return TRUE;
     }
+    else if(SvNOK(sv)) {
+        return S_nv_is_integer(aTHX_ SvNVX(sv));
+    }
     return FALSE;
 }