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/100-fix-momit-leaf-frame-pointer-error.patch

@@ -0,0 +1,16 @@
+diff --git a/yarpl/CMakeLists.txt b/yarpl/CMakeLists.txt
+--- a/yarpl/CMakeLists.txt       Fri May 03 07:45:18 2019 -0700
++++ b/yarpl/CMakeLists.txt       Tue May 07 02:03:23 2019 -0700
+@@ -21,7 +21,11 @@
+   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wextra -Wno-unused-parameter")
+   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-weak-vtables -Wno-padded")
+   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-omit-frame-pointer")
+-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -momit-leaf-frame-pointer")
++  include(CheckCXXCompilerFlag)
++  CHECK_CXX_COMPILER_FLAG("-momit-leaf-frame-pointer" HAVE_OMIT_LEAF_FRAME_POINTER)
++  if(HAVE_OMIT_LEAF_FRAME_POINTER)
++    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -momit-leaf-frame-pointer")
++  endif()
+ endif()
+
+ if(YARPL_WRAP_SHARED_IN_LOCK)

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)