These files are used by a program called aclocal (part of the GNU automake package) which uses them to create aclocal.m4 which is in turn used by autoconf to create the configure script at the the top level in this distribution. (Actually, as we need to change a few `standard' macros, we need to create acinclude.m4 by concatenating all m4 files in this directory before running aclocal.) The files are as follows. R.m4 contains R specific macros. Some of these might be useful for other systems as well, but we first need to split this into pieces. R_BLAS_LIBS is based on the AC_ARG_WITH(fastblas) code from Octave, but with tests for Alpha CXML/DXML and IRIX SCSL and SGIMATH libraries commented out. Some macros do not conform to the Autoconf $PKG_$CATEGORY_$FOO naming scheme. These test for `features' such as GNOME, zlib, etc., are named R_$FEATURE, and typically define HAVE_$FEATURE. clibs.m4 versions of the autoconf macros to find the Fortran libraries amended to find the C libraries (for comparison with the Fortran ones). codeset.m4 is from GNU gettext and checks whether nl_langinfo(CODESET) is available in langinfo.h. gettext.m4 a concatenation of all the required files from gettext 0.14.5 except codeset.m4. gettext-lib.m4 a concatenation of the m4 files from gettext-0.14.5/autoconf-lib-link. libtool.m4 is from libtool 1.5.6.