fixes for Debian 9

- search for libdwarf.h in new locations (e.g., /usr/include/libdwarf/)
- build Bochs with -std=gnu++98 (gnu++14 is default since GCC 6.1)
- specify "proto2" syntax for protobuf messages
- minor build-system and C++ namespace fixes

Change-Id: I16dbc622c797ef8e936fe3c0fb9b03029d27529d

src/core/util/llvmdisassembler/testing/llvmDisTest.cc

@@ -23,7 +23,7 @@ int main(int argc, char* argv[]) {
 	}
 
 	OwningPtr<Binary> binary;
-	if (error_code ec = createBinary(file, binary)) {
+	if (llvm::error_code ec = createBinary(file, binary)) {
 		std::cerr << "Dis" << ": '" << file << "': " << ec.message() << ".\n";
 		return -1;
 	}