xgettext: Recognize text blocks in Java parser.
* autogen.sh (GNULIB_MODULES_TOOLS_FOR_SRC): Add
unictype/syntax-java-whitespace.
* gettext-tools/src/x-java.c: Include unictype.h.
(strip_indent): New function.
(phase5_get): Parse text blocks (Java 13 syntax).
* gettext-tools/tests/xgettext-java-2: Add tests of text blocks.
* gettext-tools/doc/gettext.texi (Java): Mention the text block syntax.
* NEWS: Mention the change.
