xgettext: Scheme: Recognize hexadecimal escape sequences in string literals.
* gettext-tools/src/x-scheme.c (accumulate_escaped): Recognize \x, \u, \U escape
sequences.
* gettext-tools/tests/xgettext-scheme-7: Test also some \x escape sequences.
* gettext-tools/tests/xgettext-scheme-8: Test also some \x, \u, \U escape
sequences.
