revert: extend.texi (PowerPC Built-in Functions): Rename this subsection.

revert: extend.texi (PowerPC Built-in Functions): Rename this subsection.

2018-05-08  Kelvin Nilsen  <kelvin@gcc.gnu.org>

	Revert:
	* doc/extend.texi (PowerPC Built-in Functions): Rename this
	subsection.
	(Basic PowerPC Built-in Functions): The new name of the
	subsection previously known as "PowerPC Built-in Functions".
	(Basic PowerPC Built-in Functions Available on all Configurations):
	New subsubsection.
	(Basic PowerPC Built-in Functions Available on ISA 2.05): New
	subsubsection.
	(Basic PowerPC Built-in Functions Available on ISA 2.06): New
	subsubsection.
	(Basic PowerPC Built-in Functions Available on ISA 2.07): New
	subsubsection.
	(Basic PowerPC Built-in Functions Available on ISA 3.0): New
	subsubsection.

From-SVN: r260065