xgettext: Smalltalk: Recognize string concatenation.
* gettext-tools/src/x-smalltalk.c (struct token_ty): Add field 'comment'.
(free_token): New function.
(phase2_get): Fill in tp->comment.
(phase3_pushback): Increase size.
(phase3_get): Fill in tp->comment. Do reference counting.
(string_concat_free1): New function.
(phase4_pushback, phase4_pushback_length): New variables.
(phase4_get, phase4_unget): New functions.
(extract_smalltalk): Initialize phase4_pushback_length. Call phase4_get instead
of phase3_get, phase4_unget instead of phase3_unget. Use the comment stored in
the token. Call free_token.
* gettext-tools/tests/xgettext-smalltalk-1: Add a test case of string
concatenation.
* NEWS: Mention the improvement.
