Fix build since llvm r286566 and require at least llvm 4.0

llvm-svn: 286634
diff --git a/libclc/configure.py b/libclc/configure.py
index 9626f0e..f26f535 100755
--- a/libclc/configure.py
+++ b/libclc/configure.py
@@ -69,8 +69,8 @@
 llvm_int_version = int(llvm_version[0]) * 100 + int(llvm_version[1]) * 10
 llvm_string_version = 'LLVM' + llvm_version[0] + '.' + llvm_version[1]
 
-if llvm_int_version < 390:
-    print "libclc requires LLVM >= 3.9"
+if llvm_int_version < 400:
+    print "libclc requires LLVM >= 4.0"
     sys.exit(1)
 
 llvm_system_libs = llvm_config(['--system-libs'])