* Documentation/user/basic-notation.itely (Explicitly

* Documentation/user/basic-notation.itely (Explicitly
instantiating voices): idem.

* Documentation/user/advanced-notation.itely (Text spanners):
remove stray { }

* lily/context.cc (default_child_context_name): the default child
is now first in accepts_list_.

* ly/engraver-init.ly (RemoveEmptyRhythmicStaffContext): add
\defaultchild to all relevant contexts.  This fixes default voices
for \drums { } . Most probably, this also fixes similar problems
with ancient transcriptions getting CueVoices instead of the
desired voices.

* lily/context-def.cc (get_default_child): new function.
(get_accepted): place default child in front of list.

* lily/parser.yy (FIXME): add DEFAULTCHILD token.

* lily/include/context-def.hh (struct Context_def): add
default_accept_