Fix build with g++ 4.3

This change fixes the build for g++ 4.3. Build verified on openSUSE Factory.
Only missing includes and using directives are added.

src/FocusableList.cc

@@ -31,6 +31,12 @@
 
 #include <vector>
 
+#ifdef HAVE_CSTRING
+  #include <cstring>
+#else
+  #include <string.h>
+#endif
+
 using std::string;
 using std::vector;
 

src/FocusableList.hh

@@ -30,6 +30,7 @@
 
 #include <list>
 #include <string>
+#include <memory>
 
 class BScreen;
 class Focusable;

src/Layer.hh

@@ -25,6 +25,12 @@
 #include <string>
 #include <cstdio>
 
+#ifdef HAVE_CSTRING
+  #include <cstring>
+#else
+  #include <string.h>
+#endif
+
 using std::string;
 
 /** 

src/Xutil.cc

@@ -29,7 +29,14 @@
 #include <X11/Xatom.h>
 #include <iostream>
 
+#ifdef HAVE_CSTRING
+  #include <cstring>
+#else
+  #include <string.h>
+#endif
+
 using std::string;
+using std::strlen;
 
 #ifdef DEBUG
 using std::cerr;

util/fluxbox-update_configs.cc

@@ -48,6 +48,7 @@
 #include <fstream>
 #include <set>
 #include <map>
+#include <cstdlib>
 #include <list>
 
 using std::cout;
@@ -59,6 +60,8 @@ using std::ofstream;
 using std::set;
 using std::map;
 using std::list;
+using std::exit;
+using std::getenv;
 
 string read_file(string filename);
 void write_file(string filename, string &contents);