[FFmpeg-devel] Add libtwolame cppflags in 'configure' to prevent the use of '--extra-cflags'

[Reino Wijnsma]

I just tried to build a shared LibTwoLAME, but it gave me errors.
Building a shared LibModplug proved more successful.
FFmpeg's 'configure' didn't have any problems with it and finished
without errors.

LibOpenJPEG
<https://github.com/FFmpeg/FFmpeg/blob/master/configure#L5834-L5839> was
the reason for me to submit these patches as it already has added cppflags.