Configure: fixed detection of newer Apple clang compilers.

auto/cc/clang

@@ -5,8 +5,8 @@
 # clang
 
 
-NGX_CLANG_VER=`$CC -v 2>&1 | grep 'clang version' 2>&1 \
-                           | sed -e 's/^.*clang version \(.*\)/\1/'`
+NGX_CLANG_VER=`$CC -v 2>&1 | grep '\(clang\|LLVM\) version' 2>&1 \
+                           | sed -e 's/^.* version \(.*\)/\1/'`
 
 echo " + clang version: $NGX_CLANG_VER"
 

auto/cc/name

@@ -67,7 +67,7 @@ elif `$CC -v 2>&1 | grep 'gcc version' >/dev/null 2>&1`; then
     NGX_CC_NAME=gcc
     echo " + using GNU C compiler"
 
-elif `$CC -v 2>&1 | grep 'clang version' >/dev/null 2>&1`; then
+elif `$CC -v 2>&1 | grep '\(clang\|LLVM\) version' >/dev/null 2>&1`; then
     NGX_CC_NAME=clang
     echo " + using Clang C compiler"