multimedia/streamlink: add missing requisites

https://streamlink.github.io/install.html#dependencies

- py-pysocks is a mandatory dependency (the import isn't guarded
  by try...except)
- ffmpeg and rtmpdump are formally optional,
  but required for high-profile streaming sites, make them
  options enabled by default
- add PORTREVISION=1 to pull pysocks in.

multimedia/streamlink/Makefile

@@ -2,6 +2,7 @@
 
 PORTNAME=	streamlink
 PORTVERSION=	1.4.1
+PORTREVISION=	1
 CATEGORIES=	multimedia
 MASTER_SITES=	CHEESESHOP
 PKGNAMEPREFIX=	${PYTHON_PKGNAMEPREFIX}
@@ -14,6 +15,7 @@ LICENSE_FILE=	${WRKSRC}/LICENSE
 
 RUN_DEPENDS=	${PYTHON_PKGNAMEPREFIX}isodate>0:devel/py-isodate@${PY_FLAVOR} \
 		${PYTHON_PKGNAMEPREFIX}pycryptodome>=3.4.3:security/py-pycryptodome@${PY_FLAVOR} \
+		${PYTHON_PKGNAMEPREFIX}pysocks>0:net/py-pysocks${PY_FLAVOUR} \
 		${PYTHON_PKGNAMEPREFIX}requests>0:www/py-requests@${PY_FLAVOR} \
 		${PYTHON_PKGNAMEPREFIX}websocket-client>0:www/py-websocket-client@${PY_FLAVOR}
 
@@ -32,17 +34,19 @@ USE_PYTHON=	autoplist concurrent distutils
 
 NO_ARCH=	yes
 
-OPTIONS_DEFINE=		PYCOUNTRY
-OPTIONS_DEFAULT=
+OPTIONS_DEFINE=		FFMPEG PYCOUNTRY RTMPDUMP
+OPTIONS_DEFAULT=	FFMPEG RTMPDUMP
 .if !exists(../../textproc/py-iso3166/Makefile)
 OPTIONS_DEFAULT+=	PYCOUNTRY
 .endif
 PYCOUNTRY_DESC=		Use pycountry instead of py-iso-639 and py-iso3166
 
+FFMPEG_RUN_DEPENDS=		ffmpeg:multimedia/ffmpeg
 PYCOUNTRY_RUN_DEPENDS=		${PYTHON_PKGNAMEPREFIX}country>0:devel/py-country@${PY_FLAVOR}
 PYCOUNTRY_RUN_DEPENDS_OFF=	${PYTHON_PKGNAMEPREFIX}iso-639>0:textproc/py-iso-639@${PY_FLAVOR} \
 				${PYTHON_PKGNAMEPREFIX}iso3166>0:textproc/py-iso3166@${PY_FLAVOR}
 PYCOUNTRY_MAKE_ENV=		STREAMLINK_USE_PYCOUNTRY=1
+RTMPDUMP_RUN_DEPENDS=		rtmpdump:multimedia/rtmpdump
 
 do-test:	.PHONY
 		cd ${WRKSRC} && ${SETENV} PYTHONPATH=${WRKSRC}/src ${PYTHON_CMD} -u -m pytest -v -ra \