Extend locations where to seach for Fortran pre-include.

Extend locations where to seach for Fortran pre-include.

2019-01-16  Martin Liska  <mliska@suse.cz>

	* Makefile.in: Set TOOL_INCLUDE_DIR and NATIVE_SYSTEM_HEADER_DIR
	for GCC driver.
	* config/gnu-user.h (TARGET_F951_OPTIONS): Add 'finclude%s/' as
	a new argument.
	* gcc.c (add_sysrooted_hdrs_prefix): New function.
	(path_prefix_reset): Move up in the source file.
	(find_fortran_preinclude_file): Make complex search for the
	fortran header files.

From-SVN: r267967