Add a InitSections method to the streamer interface.

The ELF implementation now creates text, data and bss to match the gnu as
behavior.

The text streamer still has the old MachO specific behavior since
the testsuite checks that it will error when a directive is given
before a setting the current section for example.

A nice benefit is that -n is not required anymore when producing
ELF files.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@114027 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/MC/MCNullStreamer.cpp b/lib/MC/MCNullStreamer.cpp
index f7a2f20..b2db410 100644
--- a/lib/MC/MCNullStreamer.cpp
+++ b/lib/MC/MCNullStreamer.cpp
@@ -25,6 +25,9 @@
     /// @name MCStreamer Interface
     /// @{
 
+    virtual void InitSections() {
+    }
+
     virtual void SwitchSection(const MCSection *Section) {
       PrevSection = CurSection;
       CurSection = Section;