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

[Rafael Espíndola]

In order to make comdats always explicit in the IR, we decided to make
the syntax a bit more compact for the case o 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 attached patch changes the syntax to

@foo = comdat $foo global i32 0

and

declare comdat $foo void @foo

and as a syntactic sugar

$foo = comdat ...
@foo = comdat global ...

is now equivalent to

$foo = comdat ...
@foo = comdat $foo global ...

and

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

is now equivalent to

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

It would be possible to take this one step further and make

@foo = comdat global ...

equivalent to

$foo = comdat any
@foo = comdat $foo global ...

but it is not clear if that is worth it. It would require rejecting things like

$foo = comdat largest
@foo = comdat global...

Maybe as an independent patch we could make all

$foo = comdat any

optional instead?

Cheers,
Rafael
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