tccpp: allow .. in token stream

for gas comments lonely on a line such as

    # .. more stuff

where tcc would try to parse .. as a preprocessor directive

See also: 0b3612631f

tccpp.c

@@ -2549,10 +2549,13 @@ maybe_newline:
             goto parse_num;
         } else if (c == '.') {
             PEEKC(c, p);
-            if (c != '.')
-		expect("'.'");
-            PEEKC(c, p);
+            if (c == '.') {
+                p++;
                 tok = TOK_DOTS;
+            } else {
+                *--p = '.'; /* may underflow into file->unget[] */
+                tok = '.';
+            }
         } else {
             tok = '.';
         }