update .gitignore
Remove unneccesary headers, add const keywords, edit formatting.
add additional files
add const keywords, remove unnecessary header file,
improve formatting.
edit formatting, add const keywords, edit includes.
Remove unnecessary header file
Remove stack-freeing operations included in Unix-only file "Rinterface.h"
Remove Unix-only flag
Update configure file with new version number. configure is generated with a newer version of GNU Autoconf.