Clang format fixes

[pmolodo]

A few clang-format related tweaks, in preparation of running on whole repo:

• made line break before open-brace for classes (Test - apply clang-format to repo (no intent on merging it yet) #690 (comment))
• replaced MAYAUSD_NS_DEF with namesapce MAYAUSD_NS (Test - apply clang-format to repo (no intent on merging it yet) #690 (comment))
• protected some nicely-indented #if formatting in lib/mayaUsd/base/api.h

[ppt-adsk]

Hey @pmolodo, thanks for doing this. My only concern is with replacing MAYAUSD_NS_DEF with MAYAUSD_NS. You've expanded out the namespace token, which is the right thing to do for clang-format. However, MAYAUSD_NS is the namespace that is unversioned, while MAYAUSD_VERSIONED_NS is the versioned namespace. Perhaps we can question whether symbols in the maya-usd namespace need to be versioned or not; because maya-usd defines a core library that can be used by more than one plugin I would tend to err on the safe side and version them.

Also, MAYAUSD_NS_DEF abstracted away whether we were doing a Doxygen build or not --- and of course we're currently not doing anything of the sort. But again, since maya-usd is defining a core library, it doesn't seem outlandish to think we some day may want to do such a thing.

My suggestion would be to keep MAYAUSD_NS_DEF and simply take the namespace token out of it. Hope this makes sense.

[pmolodo]

Ah, makes sense. Well... should we consider just making a new macro for the non-namespace-token version? Mostly to preserve backward-compatibility for dependent code already using MAYAUSD_NS_DEF (and which may not use clang-format)?

[kxl-adsk]

We favor the non-namespace-token version because of clang-format and refactoring the code after the change is trivial. Keeping both, IMHO may be confusing for developers.

With the above, I can't find reasons for preserving backward-compatibility.

[kxl-adsk]

Thank you, @pmolodo. LGTM!

[ppt-adsk]

Thanks for doing this @pmolodo, very appreciated. Just this last nit-pick and I think we're done.

[ppt-adsk]

This comment is no longer accurate, right? We should restore the previous comment, perhaps fixing it to change the plural "Macros" to "Macro".

[kxl-adsk]

@pmolodo PF failed on all platforms - looks like changes went in that are were using the macro. Please merge the latest changes from dev and fix compilation errors.

[pmolodo]

Fixed the comment and rebased against latest dev. Tested that it compiles.