improve Visual Studio readme.txt file description of DLL use
Merge branch 'master' of https://github.com/wbhart/mpir
Merge branch 'master' of https://github.com/wbhart/mpir
add the mpn_mul_fft function (needed by GMP-ECM) and update Windows builds accordingly
update Visual Studio solution file
Add mpn_mul_fft for GMP_ECM.