Add guards to prevent typedefs when C++11 is available.

extern "C" {

// Definitions exist in C++11

#if defined __cplusplus && __cplusplus < 201103L

typedef uint32_t char32_t;

typedef uint16_t char16_t;

#endif

// Standard string functions on char16_t strings.

int strcmp16(const char16_t *, const char16_t *);