okayed on jabber.

with fixing Conflicts for:
	src/lib/dns/gen-rdatacode.py.in
	src/lib/dns/tests/rdata_txt_like_unittest.cc

with fixing Conflicts for
	src/lib/dns/gen-rdatacode.py.in
	src/lib/dns/rdata.cc
	src/lib/dns/rrparamregistry-placeholder.cc
	src/lib/dns/tests/rdata_hinfo_unittest.cc
	src/lib/dns/tests/rdata_txt_like_unittest.cc

this is actually ensured by the C++ standard lib spec.

due to limitation of the current implementation it doesn't work right now,
so commented out; planning to create a ticket to fix the underlying issue.

assert() should be okay, but that depends on details of other classes, so
exception is probably a bit safer.

some tests needed to be adjusted:
- ' ' * 256 (in python) now doesn't work as intended; they are considered
  space
- in auth tests, make sure txt RDATA containing a space is explicitly double
  quoted
- in Rdata_TXT_LIKE_Test::createFromText, removed the last test case because
  it's actually a valid representation as commented.  now the implementation
  correctly accepts it.

these are (indirectly) necessary for building external programs.

it's incomplete, but pass some tests

when we migrate the complete lexer version, this will cause confusion:
the lexer will consider the space as a separater.