Fix some MSVC warnings about possible truncation of int -> char.

tests/preprocessor_tests/char_test.cpp

@@ -41,7 +41,7 @@ bool isWhitespace(char c)
 
 TEST_P(CharTest, Identified)
 {
-    std::string str(1, GetParam());
+    std::string str(1, static_cast<char>(GetParam()));
     const char* cstr = str.c_str();
     int length = 1;
 

tests/preprocessor_tests/identifier_test.cpp

@@ -145,17 +145,17 @@ INSTANTIATE_TEST_CASE_P(A_Z_0_9,
 TEST_F(IdentifierTest, AllLetters)
 {
     std::string str;
-    for (int c = 'a'; c <= 'z'; ++c)
+    for (char c = 'a'; c <= 'z'; ++c)
         str.push_back(c);
 
     str.push_back('_');
 
-    for (int c = 'A'; c <= 'Z'; ++c)
+    for (char c = 'A'; c <= 'Z'; ++c)
         str.push_back(c);
 
     str.push_back('_');
 
-    for (int c = '0'; c <= '9'; ++c)
+    for (char c = '0'; c <= '9'; ++c)
         str.push_back(c);
 
     expectIdentifier(str);