srt-vtt: init at 2019-01-03 (#70885)

* srt-vtt: init at 2019-01-03

* Append 'unstable' to pname

Co-Authored-By: Marek Mahut <marek.mahut@gmail.com>

* Fix version

* Remove which validation

* Add support to linux only

Co-Authored-By: Evils-Devils <30512529+Evils-Devils@users.noreply.github.com>

pkgs/tools/cd-dvd/srt-to-vtt-cl/fix-validation.patch

@@ -0,0 +1,13 @@
+--- a/Makefile
++++ b/Makefile
+@@ -1,9 +1,4 @@
+-ERR = $(shell which clang++ >/dev/null; echo $$?)
+-ifeq "$(ERR)" "0"
+-	CXX ?= clang++
+-else
+-	CXX ?= g++
+-endif
++CXX ?= g++
+ CXXFLAGS = -std=c++11 -O2 -MMD -I ./deps
+ OBJECTS := src/text_encoding_detect.o src/Utils.o src/Converter.o src/main.o
+ DEPENDS := $(OBJECTS:.o=.d)