Fix CR being rejected when used as whitespace

Missed this comment from ziglang/zig-spec#83:

> CR used as whitespace, whether directly preceding NL or stray, is still unambiguously whitespace. It is accepted by the grammar and replaced by the canonical whitespace by zig fmt.

Author: moosichu

lib/std/zig/tokenizer.zig

@@ -442,7 +442,7 @@ pub const Tokenizer = struct {
             switch (state) {
                 .start => switch (c) {
                     0 => break,
-                    ' ', '\n', '\t' => {
+                    ' ', '\n', '\t', '\r' => {
                         result.loc.start = self.index + 1;
                     },
                     '"' => {
@@ -565,18 +565,6 @@ pub const Tokenizer = struct {
                         state = .int_literal_dec;
                         result.tag = .integer_literal;
                     },
-                    '\r' => {
-                        // Carriage returns are *only* allowed just before a linefeed as part of a CRLF pair, otherwise
-                        // they constitute an illegal byte!
-                        if (self.index + 1 < self.buffer.len and self.buffer[self.index + 1] == '\n') {
-                            result.loc.start = self.index + 1;
-                        } else {
-                            result.tag = .invalid;
-                            result.loc.end = self.index;
-                            self.index += 1;
-                            return result;
-                        }
-                    },
                     else => {
                         result.tag = .invalid;
                         result.loc.end = self.index;