ld: Add --enable-textrel-check=[no|yes|warning|error]

ld: Add --enable-textrel-check=[no|yes|warning|error]

Add a configure option, --enable-textrel-check=[no|yes|warning|error],
to decide what ELF linker should do by default with DT_TEXTREL in an
executable or shared library.

	PR ld/20824
	* NEWS: Mention --enable-textrel-check=[no|yes|warning|error].
	* configure.ac: Add --enable-textrel-check=[no|yes|warning|error].
	(DEFAULT_LD_TEXTREL_CHECK): New AC_DEFINE_UNQUOTED.
	(DEFAULT_LD_TEXTREL_CHECK_WARNING): Likewise.
	* ldmain.c (main): Initialize link_info.textrel_check to
	DEFAULT_LD_TEXTREL_CHECK.
	* lexsup.c (ld_options): Check DEFAULT_LD_TEXTREL_CHECK_WARNING.
	* config.in: Regenerated.
	* configure: Likewise.