When the lexer processed a backslash introducing a string escape directly
at the buffer boundary, the backslash was incorrectly retained.

-- Testcase --
{%
	print("abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijkl\n");
%}
-- End --

-- Expect stdout --
abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijkl
-- End --