debug: replaced C casts with C++ casts, doc & style tidy.
CharBuf, CharacterRange, CharacterSet: doc & style tidy.
ScriptParserException: specify noexcept and override on dtor.
config: added DUCT_CONFIG_NO_BYTESWAP_HEADER; style tidy.

test/premake:
    default to -std=c++11 under Linux;
    define DUCT_CONFIG_NO_BYTESWAP_HEADER under GCC;
    style tidy.
IO: satisfy GCC enumeral-nonenumeral comparison error/warning¹.

1: Whyyy.
test/utils/endian: align fields properly; style tidy.