winsup/doc: Convert cygwin-api function documentation to refentry elements

winsup/doc: Convert cygwin-api function documentation to refentry elements

Convert cygwin-api from using a sect2 element to using a refentry element for
each function.  This makes it possible to generate manpage-style output for
those elements.

Note that the chunked html now generates a page for each function, rather than
one containing all functions.

Also:

Remove pointless and incorrect date

Move introductory paragraph from the first section to the start of the chapter

Add a funcsynopsisinfo element with the header file to be included to each
function prototype

Remove extern "C" which doesn't process into all formats successfully

2015-06-17  Jon Turney  <jon.turney@dronecode.org.uk>

	* cygwin-api.xml: Move introductory paragraph here.
	* logon-funcs.xml: Convert from using a sect2 element to using a
	refentry element for each function.
	* misc-funcs.xml: Ditto.
	* path.xml: Ditto.

Signed-off-by: Jon TURNEY <jon.turney@dronecode.org.uk>