librsocket-cpp: Add new package librsocket-cpp

C++ implementation of RSocket
RSocket is a binary protocol for use on byte stream transports such as
TCP, WebSockets, and Aeron. (https://rsocket.io/)

This ships with two separte libraries, yarpl and rsocket

Patch 100 is already upstream
(https://github.com/rsocket/rsocket-cpp/commit/862202c6e99a49a8cbd304644d98d3f419b429d8).
Patch 101 in process of upstreaming as it needs to made compatible with
using both gold and ld.

[Dependency of https://github.com/facebook/openr]

Compile tested: openwrt master - nbg6817, arc700

Signed-off-by: Amol Bhave <ambhave@fb.com>

libs/librsocket-cpp/patches/101-do-not-use-gold.patch

@@ -0,0 +1,11 @@
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -67,7 +67,6 @@
+   if (RSOCKET_ASAN)
+     set(ASAN_FLAGS -fsanitize=address,undefined)
+   endif ()
+-  set(EXTRA_LINK_FLAGS ${EXTRA_LINK_FLAGS} -fuse-ld=gold)
+
+ elseif (${CMAKE_CXX_COMPILER_ID} MATCHES Clang)
+   if (RSOCKET_ASAN)