for consistency with used coding conventions.

Declarations for shared library in Windows.

Added __declspec(dllimport) and __declspec(dllexport) declarations
when compiled in Windows.

because the memory areas may overlap.

~20% faster compile time on bloat-test

Fix fileno causing compile error when #defined

Error:
expected unqualified-id before '(' token
 int fmt::BufferedFile::fileno() const {

This is an issue with Android NDK and mingw32.

and improve naming consistency

Silence some performance warnings in Visual Studio

Older Visual Studio versions are not shipped with stdint.h

in custom stream buffer implementation:

* basic_formatbuf -> internal::FormatBuf
* remove unused Traits template argument