[Libva] [PATCH] add replacement for log2f when not available

[Xiang, Haihao]

Applied, Thx

> From: Adrian Marius Negreanu <adrian.m.negreanu at intel.com>
> 
> Signed-off-by: Adrian Marius Negreanu <adrian.m.negreanu at intel.com>
> ---
>  configure.ac          | 1 +
>  src/gen6_mfc_common.c | 4 ++++
>  2 files changed, 5 insertions(+)
> 
> diff --git a/configure.ac b/configure.ac
> index 176519d..a9ed8d5 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -65,6 +65,7 @@ AC_C_BIGENDIAN
>  AC_HEADER_STDC
>  AC_SYS_LARGEFILE
>  AC_CHECK_LIB([m], [sin])
> +AC_CHECK_FUNCS([log2f])
>  
>  LIBVA_PACKAGE_VERSION=libva_package_version
>  AC_SUBST(LIBVA_PACKAGE_VERSION)
> diff --git a/src/gen6_mfc_common.c b/src/gen6_mfc_common.c
> index bb5d360..1d57075 100644
> --- a/src/gen6_mfc_common.c
> +++ b/src/gen6_mfc_common.c
> @@ -62,6 +62,10 @@
>  
>  #define BRC_PI_0_5 1.5707963267948966192313216916398
>  
> +#ifndef HAVE_LOG2F
> +#define log2f(x) (logf(x)/(float)M_LN2)
> +#endif
> +
>  static void
>  intel_mfc_bit_rate_control_context_init(struct encode_state *encode_state, 
>                                         struct gen6_mfc_context *mfc_context)