json: Eliminate lexer state IN_WHITESPACE, pseudo-token JSON_SKIP

The lexer ignores whitespace like this:

         on whitespace      on non-ws   spontaneously
    IN_START --> IN_WHITESPACE --> JSON_SKIP --> IN_START
                    ^    |
                     \__/  on whitespace

This accumulates a whitespace token in state IN_WHITESPACE, only to
throw it away on the transition via JSON_SKIP to the start state.
Wasteful.  Go from IN_START to IN_START on whitespace directly,
dropping the whitespace character.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180831075841.13363-7-armbru@redhat.com>

qobject/json-parser-int.h

@@ -31,7 +31,6 @@ typedef enum json_token_type {
     JSON_KEYWORD,
     JSON_STRING,
     JSON_INTERP,
-    JSON_SKIP,
     JSON_END_OF_INPUT,
     JSON_MAX = JSON_END_OF_INPUT
 } JSONTokenType;