d: Make TARGET_D_MINFO_SECTION hooks in elfos.h the language default.

Removes the last of all TARGET_D_* macro definitions in common target
headers.  Now everything is either defined in the D language front-end,
or D-specific target headers.

gcc/ChangeLog:

	* config/darwin-d.cc (TARGET_D_MINFO_START_NAME): Rename to ...
	(TARGET_D_MINFO_SECTION_START): ...this.
	(TARGET_D_MINFO_END_NAME): Rename to ...
	(TARGET_D_MINFO_SECTION_END): ... this.
	* config/elfos.h (TARGET_D_MINFO_SECTION): Remove.
	(TARGET_D_MINFO_START_NAME): Remove.
	(TARGET_D_MINFO_END_NAME): Remove.
	* config/i386/cygwin-d.cc (TARGET_D_MINFO_SECTION): Remove.
	(TARGET_D_MINFO_START_NAME): Remove.
	(TARGET_D_MINFO_END_NAME): Remove.
	* config/i386/winnt-d.cc (TARGET_D_MINFO_SECTION): Remove.
	(TARGET_D_MINFO_START_NAME): Remove.
	(TARGET_D_MINFO_END_NAME): Remove.
	* doc/tm.texi: Regenerate.
	* doc/tm.texi.in (TARGET_D_MINFO_START_NAME): Rename to ...
	(TARGET_D_MINFO_SECTION_START): ...this.
	(TARGET_D_MINFO_END_NAME): Rename to ...
	(TARGET_D_MINFO_SECTION_END): ...this.

gcc/d/ChangeLog:

	* d-target.def (d_minfo_section): Expand documentation of hook.
	Default initialize to "minfo".
	(d_minfo_start_name): Rename to ...
	(d_minfo_section_start): ... this.  Default initialize to
	"__start_minfo".
	(d_minfo_end_name): Rename to ...
	(d_minfo_section_end): ... this. Default initialize to "__stop_minfo".
	* modules.cc (register_moduleinfo): Use new targetdm hook names.