xgettext: In language Java, avoid stack overflow.
* gettext-tools/src/x-java.c (MAX_NESTING_DEPTH): New macro.
(paren_nesting_depth, brace_nesting_depth): New variables.
(extract_parenthesized): Increase and check paren_nesting_depth or
brace_nesting_depth before calling extract_parenthesized recursively.
(extract_java): Initialize paren_nesting_depth and brace_nesting_depth.
* gettext-tools/tests/xgettext-java-stackovfl-1: New file.
* gettext-tools/tests/xgettext-java-stackovfl-2: New file.
* gettext-tools/tests/xgettext-java-stackovfl-3: New file.
* gettext-tools/tests/xgettext-java-stackovfl-4: New file.
* gettext-tools/tests/Makefile.am (TESTS): Add them.
