[NEON] warning: redefinition of typedef 'float16_t' is a C11 feature [-Wtypedef-redefinition]

[dgazzoni]

Consider the following, essentially empty, file:

#define SIMDE_ENABLE_NATIVE_ALIASES
#include "arm/neon.h"

int main() {
    return 0;
}

Compiling this with Apple's clang version using the -std=gnu99 flag produces the following compilation error:

.../arm/neon/types.h:941:33: warning: redefinition of typedef 'float16_t' is a C11 feature [-Wtypedef-redefinition]
  typedef   simde_float16_t     float16_t;
                                ^
.../arm/neon/types.h:857:33: note: previous definition is here
  typedef   simde_float16_t     float16_t;

Header files are obtained from the 647dc12 commit. A pull request will soon follow.