config.mingw: get fmt_pid quoting correct
config.mingw: get fmt_pid quoting correct

Fallout from earlier changes in configure.ac and src/include/pcp/*

adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp