swr: relax c++ requirement from c++14 to c++11

Remove c++14 generic lambda to keep compiler requirement at c++11.

No regressions on piglit or vtk test suites.

Tested-by: Chuck Atkins <chuck.atkins@kitware.com>
Reviewed-by: Bruce Cherniak <bruce.cherniak@intel.com>

CC: mesa-stable@lists.freedesktop.org
diff --git a/configure.ac b/configure.ac
index 5caf316..82a1bd6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2472,10 +2472,10 @@
         xswr)
             llvm_require_version $LLVM_REQUIRED_SWR "swr"
 
-            swr_require_cxx_feature_flags "C++14" "__cplusplus >= 201402L" \
-                "-std=c++14" \
-                SWR_CXX14_CXXFLAGS
-            AC_SUBST([SWR_CXX14_CXXFLAGS])
+            swr_require_cxx_feature_flags "C++11" "__cplusplus >= 201103L" \
+                ",-std=c++11" \
+                SWR_CXX11_CXXFLAGS
+            AC_SUBST([SWR_CXX11_CXXFLAGS])
 
             swr_require_cxx_feature_flags "AVX" "defined(__AVX__)" \
                 ",-mavx,-march=core-avx" \