devel/py-breathe: fix alternative Python versions

The port used to build only for the default python version,
use BINARY_ALIAS to help the build find the proper Sphinx version.

Switch to autoplist to permit packaging for Python 3.6/3.7, too
(__pycache__ layout differences don't work well with static pkg-plist).

Not bumping PORTREVISION again on the assumption that we would not have
been able to build a package previously on an alternative Python
version, so there is nothing to flush out with a PORTREVISION bump.

devel/py-breathe/Makefile

@@ -17,15 +17,20 @@ RUN_DEPENDS=	${PYTHON_PKGNAMEPREFIX}sphinx>=0,1:textproc/py-sphinx@${PY_FLAVOR}
 USES=		gmake python:3.6+
 USE_GITHUB=	yes
 GH_TUPLE=	michaeljones:breathe:v${PORTVERSION}
-USE_PYTHON=	distutils
+USE_PYTHON=	autoplist distutils
 NO_ARCH=	yes
 
+BINARY_ALIAS=	sphinx-build=sphinx-build-${PYTHON_VER}
+
 OPTIONS_DEFINE=		DOCS EXAMPLES PDFDOCS
 OPTIONS_SUB=		yes
 PDFDOCS_DESC=		Build PDF documentation (implies DOCS)
 PDFDOCS_IMPLIES=	DOCS
 PDFDOCS_BUILD_DEPENDS=	pdflatex:print/tex-formats
 
+PORTDOCS=	*
+PORTEXAMPLES=	*
+
 post-patch:
 		${REINPLACE_CMD} "s/^git_tag = subprocess.*/git_tag = b'v${PORTVERSION}'/" \
 			${WRKSRC}/documentation/source/conf.py