Change the .ll syntax for comdats and add a syntactic sugar.

In order to make comdats always explicit in the IR, we decided to make
the syntax a bit more compact for the case of a GlobalObject in a
comdat with the same name.

Just dropping the $name causes problems for

@foo = globabl i32 0, comdat
$bar = comdat ...

and

declare void @foo() comdat
$bar = comdat ...

So the syntax is changed to

@g1 = globabl i32 0, comdat($c1)
@g2 = globabl i32 0, comdat

and

declare void @foo() comdat($c1)
declare void @foo() comdat

llvm-svn: 225302
diff --git a/llvm/test/Verifier/comdat2.ll b/llvm/test/Verifier/comdat2.ll
index d78030c..9d892b9 100644
--- a/llvm/test/Verifier/comdat2.ll
+++ b/llvm/test/Verifier/comdat2.ll
@@ -1,5 +1,5 @@
 ; RUN: not llvm-as %s -o /dev/null 2>&1 | FileCheck %s
 
 $v = comdat any
-@v = private global i32 0, comdat $v
+@v = private global i32 0, comdat($v)
 ; CHECK: comdat global value has private linkage