Complete Host::Backtrace prototype.  Fixes Linux build.

git-svn-id: https://llvm.org/svn/llvm-project/llvdb/trunk@136951 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/source/Host/common/Host.cpp b/source/Host/common/Host.cpp
index f56c4b7..f88c76b 100644
--- a/source/Host/common/Host.cpp
+++ b/source/Host/common/Host.cpp
@@ -488,6 +488,7 @@
 {
 }
 
+void
 Host::Backtrace (Stream &strm, uint32_t max_frames)
 {
     // TODO: Is there a way to backtrace the current process on linux? Other systems?