Supporting removal of STRICT_R_HEADERS in 4.5.0

[yaccos]

This PR aims to resolve issue #271. The following changes have been made:

• R version requirement lifted to 3.4.0
• Macro redefinitions of Calloc and Free have been removed. All occurences of the functions have been replaced by their modern counterparts.
• The custom definition of R_XLEN_T_MAX has been removed as R >= 3.0.0 already includes this.
• 000.types.h now explicitly includes float.h as this is needed to compile with STRICT_R_HEADERS on R versions prior to 4.5.0.

[HenrikBengtsson]

Thanks. It looks like you introduced CRLF newlines to a few of the files you edited;

+#include <Rinternals.h> /* R_xlen_t, ... */^M
+#include <Rversion.h>   /* R_VERSION, R_Version() */^M

Can you please remove those, i.e. replace them with LF newlines? I think this is also why the diff rendered reports the files as changed (51246bc)

[yaccos]

I am sorry about the newline corruption, it should be fixed now. Turns out that it is a good idea to set up git to automatically convert line endings on commit.

[HenrikBengtsson]

Thanks!