aarch64: assembler in clang-3.4 ignores the division by two

Values are positive powers of two, so just replace it with right shift.
build: handle library dependencies in configure

Instead of setting FFLIBS in each library Makefile configure
exports FFLIBS-$library in config.mak.
Merge commit '9aa4592076d4dbb29d1198b0e258f9f85c0c00b5'

* commit '9aa4592076d4dbb29d1198b0e258f9f85c0c00b5':
  aarch64: assembler in clang-3.4 ignores the division by two

Merged-by: Michael Niedermayer <michaelni@gmx.at>
dpx: use intfloat.h instead of deprecated intfloat_readwrite.h.

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>
Merge commit '449511740f06a4675b0066730fa45cdb764ffafc'

* commit '449511740f06a4675b0066730fa45cdb764ffafc':
  build: handle library dependencies in configure

Conflicts:
	common.mak
	configure
	libavdevice/Makefile
	libavfilter/Makefile

Merged-by: Michael Niedermayer <michaelni@gmx.at>
common.mak: fix (not)building disabled libs

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
configure: swresample depends on avutil

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
build: move ebur128 swr dep to configure.
swscale/utils: Add check that ensures that the hardcoded struct offsets are valid

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>