lexer: Add TT_COLONDUB and putback buffer

Signed-off-by: Ian Moffett <ian@mirocom.org>

include/common/state.h

@@ -23,6 +23,7 @@
  * @lex_buf:        Used to reduce system call frequency
  * @lex_buf_cap:    Lexer buffer capacity
  * @lex_buf_i:      Lexer buffer index
+ * @lex_putback:    Lexer putback buffer
  */
 struct quip_state {
     int in_fd;
@@ -30,6 +31,7 @@ struct quip_state {
     char lex_buf[LEX_FILEBUF_LEN];
     size_t lex_buf_cap;
     size_t lex_buf_i;
+    char lex_putback;
 };
 
 /*

include/frontend/token.h

@@ -19,6 +19,7 @@ typedef enum {
     TT_NAME,        /* [name] */
     TT_NEWLINE,     /* [newline] */
     TT_COLON,       /* ':' */
+    TT_COLONDUB,    /* '::' */
 } tt_t;
 
 /*