Regex: move boost headers to top of list to work around clang issue which requires workarounds present in config.hpp.

include/boost/regex/icu.hpp

@@ -19,6 +19,7 @@
 #ifndef BOOST_REGEX_ICU_HPP
 #define BOOST_REGEX_ICU_HPP
 
+#include <boost/config.hpp>
 #include <unicode/utypes.h>
 #include <unicode/uchar.h>
 #include <unicode/coll.h>

include/boost/regex/pending/object_cache.hpp

@@ -19,12 +19,12 @@
 #ifndef BOOST_REGEX_OBJECT_CACHE_HPP
 #define BOOST_REGEX_OBJECT_CACHE_HPP
 
+#include <boost/config.hpp>
+#include <boost/shared_ptr.hpp>
 #include <map>
 #include <list>
 #include <stdexcept>
 #include <string>
-#include <boost/config.hpp>
-#include <boost/shared_ptr.hpp>
 #ifdef BOOST_HAS_THREADS
 #include <boost/regex/pending/static_mutex.hpp>
 #endif

include/boost/regex/v4/regex_workaround.hpp

@@ -19,7 +19,7 @@
 #ifndef BOOST_REGEX_WORKAROUND_HPP
 #define BOOST_REGEX_WORKAROUND_HPP
 
-
+#include <boost/config.hpp>
 #include <new>
 #include <cstring>
 #include <cstdlib>