This fixes compiling fmtlib in header-only mode when user code also has
something called 'Arg' defined. Now qualifying Arg struct with internal
namespace.

* Add default copy constructor to SystemError
* Add FMT_DEFAULTED_COPY_CTOR macro

Add join argument allowing formating list of values separated by a
string. Each value is formated according the format specifier.

When using the NDK 13b toolchain standalone or with CMake, ANDROID is not defined,
but __ANDROID__ is defined instead.

* allow to stream user defined types in a MemoryWriter

* fix indent

* follow Google C++ Style

* make code c++98 compatible

* fix macro usage

* disable ability to stream user defined types if not at least c++11

* fix for disable ability to stream user defined types if not at least c++11

* use FMT_STATIC_ASSERT

Managed C++ code doesn't have the _BitScanReverse* intrinsics, we must use the fallback code for count_digits etc.

* Allow %s as generic format specifier in printf

Signed integers are formatted as %d
Unsigned integers are formatted as %u
Doubles are formatted as %f
Chars are formatted as %c
Void Pointers are formatted as %p

* Remove '%S' handling and use visitor for generic format strings

* Default for floating point is now "%g" rather than "%f"

* A custom FormatSpec type can be passed as a template argument to the ArgFormatter chain (#439)

* Corrected nested-name-specifier error

* Spec template argument defaulted to FormatSpec

* Forward declaration of FormatSpec

* Style

* Style (part 2)

* Style (part 3)

* - added basic_string allocator support to BasicStringRef, BasicCStringRef, BasicWriter::str, StringBuffer and BasicStringWriter

* - removed templated str() and to_string() function
- code style fixes

Fixes #413.