move some common functions to common.cpp and add some functions in common
Use the right linker output parameters for codec_unittest.exe

This also includes the -nologo parameter to silence extra output
from the compiler/linker.

Also add a separating empty line between the codec_unittest rule
and the include for dependency rules.
Merge pull request #574 from ruil2/vp_update

    move some common functions to common.cpp and add some functions in c...
Remove unused *_LIBS make variables
Merge pull request #576 from mstorsjo/link-flag-cleanup

Remove unused *_LIBS make variables
Merge pull request #575 from mstorsjo/make-fixes

Use the right linker output parameters for codec_unittest.exe