Log message:
Update all R packages to canonical form.

The canonical form [1] of an R package Makefile includes the
following:

- The first stanza includes R_PKGNAME, R_PKGVER, PKGREVISION (as
  needed), and CATEGORIES.

- HOMEPAGE is not present but defined in math/R/Makefile.extension to
  refer to the CRAN web page describing the package.  Other relevant
  web pages are often linked from there via the URL field.

This updates all current R packages to this form, which will make
regular updates _much_ easier, especially using pkgtools/R2pkg.

[1] http://mail-index.netbsd.org/tech-pkg/2019/08/02/msg021711.html

Log message:
math/R-igraph: Needs a C compiler

Log message:
math/R-igraph: Import version 1.2.1

Routines for simple graphs and network analysis. It can handle large
graphs very well and provides functions for generating random and
regular graphs, graph visualization, centrality methods and much more.