Add patch to deal with c++11 on EL6.

codec2-el6_gnu11.patch

@@ -0,0 +1,31 @@
+Index: codec2-dev/CMakeLists.txt
+===================================================================
+--- codec2-dev/CMakeLists.txt	(revision 3026)
++++ codec2-dev/CMakeLists.txt	(working copy)
+@@ -52,18 +52,21 @@
+ endif()
+ 
+ # Set default C++ flags.
+-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall")
+-set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall -g -O3 -std=gnu11")
++include(CheckCCompilerFlag)
++set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall -g -O3")
++CHECK_C_COMPILER_FLAG("-std=gnu11" COMPILER_SUPPORTS_GNU11)
++if(COMPILER_SUPPORTS_GNU11)
++    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -std=gnu11")
++else()
++    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -std=gnu99")
++endif()
+ # set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wno-unused-function")
+ 
+ set(CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS}")
+-set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS}")
+ set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS}")
+-set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS}")
+ 
+ # -fPIC is implied on MinGW...
+ if(NOT WIN32)
+-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fPIC")
+     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fPIC")
+ endif()
+