Rearrange characters in whitespace string

The arrangement saves about 1.3 seconds when running the test vectors. It looks like the tab character is dominant, so we profit by listing it first.

datatest.cpp

@@ -712,20 +712,19 @@ bool GetField(std::istream &is, std::string &name, std::string &value)
 			}
 		}
 
-		// Leading, trailing and temp position. The leading position moves right, and
+		// Leading and trailing position. The leading position moves right, and
-		// trailing position moves left. The sub-string in the middle is the value for
+		// trailing position moves left. The sub-string in the middle is the value
-		// the name. We leave one space when line continuation is in effect, (and if
+		// for the name. We leave one space when line continuation is in effect.
-		// present). The value can be an empty string. One Plaintext value is often
+		// The value can be an empty string. One Plaintext value is often empty
-		// empty for algorithm testing.
+		// for algorithm testing.
 		std::string::size_type l=0, t=std::string::npos;
-		const std::string whitespace = " \r\n\t\v\f";
+		const std::string whitespace = "\t \r\n";
 
 		l = line.find_first_not_of(whitespace, l);
 		if (l == std::string::npos) { l = 0; }
 		t = line.find('#', l);
 		if (t != std::string::npos) { t--; }
-
+		t = line.find_last_not_of(whitespace, t);
-		t = line.find_last_not_of(whitespace+"\\", t);
 		if (t != std::string::npos) { t++; }
 
 		CRYPTOPP_ASSERT(t >= l);