cobol: Guard clock_gettime(). [PR119975]

cobol: Guard clock_gettime(). [PR119975]

This attempts to eliminate "'clock_gettime' not declared..." when
building on x86_64-apple-darwin15.6.0.  Calls to clock_gettime have been
reduced to two locations.  Both have been guarded with

gcc/cobol/ChangeLog:

	PR cobol/119975
	* genapi.cc (parser_intrinsic_call_0): Use get_time_nanoseconds().
	* genutil.cc (get_time_64): Rename to get_time_nanoseconds().
	(get_time_nanoseconds): Likewise.
	* genutil.h (get_time_64): Likewise.
	(get_time_nanoseconds): Likewise.
	* util.cc (class cbl_timespec): Timing routine uses
	get_time_nanoseconds().
	(operator-): Likewise.
	(parse_file): Likewise.

libgcobol/ChangeLog:

	PR cobol/119975
	* configure.ac: AC_CHECK_LIB(rt, clock_gettime).
	* config.h.in: Likewise.
	* configure: Likewise.
	* gfileio.cc: Remove in-line cppcheck-suppress.
	* intrinsic.cc (timespec_to_string): Use guarded clock_gettime().
	(__gg__current_date): Likewise.
	(__gg__seconds_past_midnight): Likewise.
	(__gg__formatted_current_date): Likewise.
	(__gg__random): Likewise.
	(__gg__random_next): Likewise.
	(__gg__when_compiled): Likewise.
	* libgcobol.cc (cobol_time): Likewise.
	(get_time_nanoseconds): Likewise.
	(__gg__clock_gettime): Likewise.
	(__gg__get_date_hhmmssff): Likewise.
	* libgcobol.h (__gg__clock_gettime): Likewise.
	(struct cbl_timespec): Likewise.