Platforms: Add arm32 and arm64 platform files

[versat]

The default is "unsigned" so i have choosen it for the platformfiles.
This can be changed via a compiler option, but i am not sure if it makes
sense to add all the platform files with "signed" also.
Since the size of wchar_t depends on the compiler i added both possible
variants respectively.
Sizes of data types can be checked here for example:
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.den0024a/ch08s02.html

[danmar]

nice! feel free to apply this.

[amai2012]

sizeof wchar_t is compiler dependent? Just an idea: Would it be helpful to name them like arm32_gcc instead?

[versat]

It is not only compiler dependent but also compiler option dependent. I missed to write that. The armcc for example sets the size of wchar_t automatically to 4 if a Linux configuration is given via command line and the size can also be set via command line flags to 2 and 4 manually, the default is 2. So this is not so easy to name it more elegant i guess 😀