use string_view in unittest_nfc. That avoids copying and makes compiler happy, too!

test/unittest_nfc.cc

@@ -9,10 +9,10 @@ namespace {
 
 struct TestEntry
 {
-	std::string input;
+	string_view input;
 	bool  is_nfc;
 	IsNFC quick;
-	std::string nfc;
+	string_view nfc;
 };
 
 typedef TestEntry TE;
@@ -46,8 +46,8 @@ const std::vector<TestEntry> testValues =
 		{ "a\xcc\x85\xcc\xbc", false,  IsNFC::No  , "a\xcc\xbc\xcc\x85"}, // a + <U+0305> + <U+033C> (overline + seagull_below)
 		{ "a\xcc\xbc\xcc\x85",  true,  IsNFC::Yes , "a\xcc\xbc\xcc\x85"}, // a + <U+033C> + <U+0305> (seagull_below + overline)
 
-		{ std::string(nullo, nullo+1), true, IsNFC::Yes, std::string(nullo, nullo+1)  },  // Yeah, 1 NUL byte
-		{ std::string(nullo, nullo+4), true, IsNFC::Yes, std::string(nullo, nullo+4)  },  // Yeah, 4 NUL bytes
+		{ string_view(nullo, 1), true, IsNFC::Yes, string_view(nullo, 1)  },  // Yeah, 1 NUL byte
+		{ string_view(nullo, 4), true, IsNFC::Yes, string_view(nullo, 4)  },  // Yeah, 4 NUL bytes
 		
 		{ "EOF", true, IsNFC::Yes, "EOF" }
 	};