Target FP: Remove unused floating-point routines

Target FP: Remove unused floating-point routines

This patch removes the following routines, which now have no remaining
users in GDB:
 - extract_typed_floating
 - store_typed_floating
 - convert_typed_floating
 - decimal_from_doublest
 - decimal_to_doublest
 - value_as_double
 - unpack_double
 - value_from_double
 - value_from_decfloat

This completes removal of DOUBLEST from all files except doublest.{c,h}
and target-float.c.

gdb/ChangeLog:
2017-11-06  Ulrich Weigand  <uweigand@de.ibm.com>

	* doublest.c: Do not include "gdbtypes.h".
	(extract_typed_floating): Remove.
	(store_typed_floating): Remove.
	(convert_typed_floating): Remove.
	* doublest.h (struct type): Remove.
	(DOUBLEST_PRINT_FORMAT): Remove.
	(DOUBLEST_SCAN_FORMAT): Remove.
	(extract_typed_floating): Remove.
	(store_typed_floating): Remove.
	(convert_typed_floating): Remove.

	* dfp.c (decimal_from_doublest): Remove.
	(decimal_to_doublest): Remove.
	* dfp.h: Do not include "doublest.h".
	(decimal_from_doublest): Remove.
	(decimal_to_doublest): Remove.

	* value.c: Do not include "doublest.h" and "dfp.h".
	(value_as_double): Remove.
	(unpack_double): Remove.
	(value_from_double): Remove.
	(value_from_decfloat): Remove.
	* value.h: Do not include "doublest.h".
	(value_as_double): Remove.
	(unpack_double): Remove.
	(value_from_double): Remove.
	(value_from_decfloat): Remove.