packages: ac_cv_prog_GTKDOC=false not 'no'
packages: also ac_cv_prog_HAVE_DOXYGEN it's a program to call
packages: don't disable alloca

I have experiences on broken alloca with mingw so it's safe to leave
as his, until some report
packages: add strerror(0) detection to cache
packages: load ac_cache once
packages: when using C=1 enable config.cache
packages: added missing cached values for iconv
packages: missing fdk-aac (headers only)
patches: sync mp (new patch fdkaac)
patches: sync ff
builds: enable fdk aac dynload via ffmpeg in mplayer
packages: add staticlib def to fdk aac