Rollup merge of rust-lang#22904 - dotdash:drop_old_clang, r=alexcrichton

 Fixes rust-lang#20467

Author: Manishearth

configure

@@ -875,7 +875,7 @@ then
             | cut -d ' ' -f 2)
 
         case $CFG_CLANG_VERSION in
-            (3.0svn | 3.0 | 3.1* | 3.2* | 3.3* | 3.4* | 3.5* | 3.6*)
+            (3.2* | 3.3* | 3.4* | 3.5* | 3.6*)
             step_msg "found ok version of CLANG: $CFG_CLANG_VERSION"
             if [ -z "$CC" ]
             then