Cycles:

* Compute MD5 hash to deal with nvidia opencl compiler cache not recognizing
  changes in #included files, makes it possible to do kernel compile only
  once and remember it for the next time blender is started.
* Kernel tweak to compile with ATI/linux. Enabling any more functionality than
  simple clay render still chokes the compiler though, without a specific error
  message ..

intern/cycles/util/util_path.cpp

@@ -17,6 +17,7 @@
  */
 
 #include "util_debug.h"
+#include "util_md5.h"
 #include "util_path.h"
 #include "util_string.h"
 
@@ -59,5 +60,29 @@ string path_join(const string& dir, const string& file)
 	return (boost::filesystem::path(dir) / boost::filesystem::path(file)).string();
 }
 
+string path_files_md5_hash(const string& dir)
+{
+	/* computes md5 hash of all files in the directory */
+	MD5Hash hash;
+
+	if(boost::filesystem::exists(dir)) {
+		boost::filesystem::directory_iterator it(dir), it_end;
+
+		for(; it != it_end; it++) {
+			if(boost::filesystem::is_directory(it->status())) {
+				path_files_md5_hash(it->path().string());
+			}
+			else {
+				string filepath = it->path().string();
+
+				hash.append((const uint8_t*)filepath.c_str(), filepath.size());
+				hash.append_file(filepath);
+			}
+		}
+	}
+
+	return hash.get_hex();
+}
+
 CCL_NAMESPACE_END