BIND 10 #2442: update TXTLikeImpl with from lexer constructor

[BIND 10 Development]

#2442: update TXTLikeImpl with from lexer constructor
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            Reporter:  jinmei        |                        Owner:
                Type:  task          |  jinmei
            Priority:  medium        |                       Status:
           Component:  libdns++      |  accepted
            Keywords:                |                    Milestone:
           Sensitive:  0             |  Sprint-20121218
         Sub-Project:  DNS           |                   Resolution:
Estimated Difficulty:  4             |                 CVSS Scoring:
         Total Hours:  0             |              Defect Severity:  N/A
                                     |  Feature Depending on Ticket:
                                     |  loadzone-ng
                                     |          Add Hours to Ticket:  0
                                     |                    Internal?:  0
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Comment (by jinmei):

 trac2442 is ready for review.

 This branch is based on snapshots of some other branches, which should
 be excluded from the review.  Specifically, the diff to be reviewed
 is 8da8a38..head (the ones marked with [2442] in commit logs).

 This branch contains two main sets of changes:

 - the implementation of `strToCharstring()` as described in the ticket
   description.  It (and its tests) is in newly created files:
   char_string.{cc,h} and rdata_char_string_unittest.cc.  These are
   independent changes, and can be reviewed separately.
 - The rest is updates to the existing `TXTLike` class using the
   function and `MasterLexer`.  I believe the changes to the class
   should be trivial.  I needed to adjust some test cases because some
   of the input for the pure std::string version that was accepted
   before is not rejected (because it now uses `MasterLexer` internally
   and performs more strict parsing).

 I've noticed there's one other case that cannot be compatible with
 BIND 9 (the commented-out test case in createMultiStringsFromText).
 That will require some non trivial changes to the lexer class and will
 affect other test cases, so I plan to defer it to a separate ticket
 (will create it).  This should be a pretty minor case anyway, so I
 believe it's okay to skip for the beta.

 Technically this branch contains a user-visible feature (supporting
 multiple char-strings in TXT-like RDATA parser), but I think it's too
 minor so don't plan to add a changelog just for this.

-- 
Ticket URL: <http://bind10.isc.org/ticket/2442#comment:5>
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