improve signed integer properties tests on arm

Author: jkotan

test/datatype/integer_test.cpp

@@ -184,7 +184,7 @@ TEMPLATE_TEST_CASE("general integer properties with cref",
 
 TEMPLATE_TEST_CASE("signed integer properties",
                    "[datatype][numeric][integer]",
-                   char,
+                   signed char,
                    short,
                    int,
                    long,
@@ -205,7 +205,7 @@ TEMPLATE_TEST_CASE("signed integer properties",
 
 TEMPLATE_TEST_CASE("signed integer properties with cref",
                    "[datatype][numeric][integer]",
-                   char,
+                   signed char,
                    short,
                    int,
                    long,