* cpplib.c (xcalloc):  From from cppalloc.c.
* cpplib.c (cpp_push_buffer):  If recursion too deap, return NULL
rather than exiting with fatal.
(make_assertion, cpp_expand_to_buffer, push_macro_expansion,
do_include, cpp_start_rea):  Handle NULL return from cpp_push_buffer.
(output_line_command):  Update position even if no_output.
        (parse_clear_mark):  Use fatal instead of abort.

From-SVN: r12207