Rename Dsymbol.namespace to cppnamespace

[edi33416]

Because Dsymbol.namespace is a public extern (C++) symbol, the C++ header generator will generate the following code

class Dsymbol : public ASTNode
{
public:
    /* ... */
    CPPNamespaceDeclaration* namespace;
    /* ... */
}

As you know, and see from the syntax highlight, namespace is a C++ keyword, so this generated code won't compile.

This PR renames only the public symbol Dsymbol.namespace.
Maybe it should rename all of the namespace occurrences?

I think, in my humble opinion, that we should avoid using other programming languages keywords as public symbols.

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[lesderid]

I think, in my humble opinion, that we should avoid using other programming languages keywords as public symbols.

Wouldn't it be a better idea to handle these issues as special cases in the respective generators?

If it's just C++ (and maybe C and Obj-C) keywords that we have to take special care with, it doesn't pose much of an issue, but it could quickly become one if we want to support other languages. For example, I just googled for a list of Go keywords and apparently range is a keyword in Go.

[Geod24]

I think, in my humble opinion, that we should avoid using other programming languages keywords as public symbols.

Well many languages have many different kind of keywords, and some are very generic. Go's range (or chan), C#'s async and await. Simula has value, comment, begin, before... Well you get the picture.
In this case, I think the generator should just append an underscore (_) like we do when a foreign language name conflicts with a D name (e.g. body)

[andralex]

Looks like special casing other languages' keywords is more roundabout - people need to run to the manual to figure how their symbols are translated. Just going for straight generation and reasonably asking for due diligence in naming seems appropriate.

[andralex]

Hm, thought it was approved and I just pushed "merge". If I was hasty lmk.