Add method raw_fd_ostream::seek() for random access within a file.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@63044 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/raw_ostream.cpp b/lib/Support/raw_ostream.cpp
index 96c9a3a..29665dc 100644
--- a/lib/Support/raw_ostream.cpp
+++ b/lib/Support/raw_ostream.cpp
@@ -255,6 +255,12 @@
   FD = -1;
 }
 
+uint64_t raw_fd_ostream::seek(uint64_t off) {
+  flush();
+  pos = lseek(FD, off, SEEK_SET);
+  return pos;  
+}
+
 //===----------------------------------------------------------------------===//
 //  raw_stdout/err_ostream
 //===----------------------------------------------------------------------===//