build: use automake as a build system

Also provide a convenient pkg-config file at the same time.
Merge remote-tracking branch 'jan-engelhardt/master'
build system: bump version number
build system: autogen.sh script for generating configure etc.
build system: add new source/header files to Makefile.am
build system: remove old build files
ChangeLog: update with build system changes
cosmetics: alignment