config: libtoolize: put macros in AC_CONFIG_MACRO_DIR, 'm4'

As suggested by one tool called by autoreconf. Necessitates change to:
- configure.ac: Call AC_CONFIG_MACRO_DIR()
- Makefile.am: Set ACLOCAL_AMFLAGS = -I m4
- Create placeholder m4 folders
- Update gitignore files

>From the autoconf documentation:

 "Starting from version 2.58, autoconf provide the macro AC_CONFIG_MACRO_DIR
  to declare where additional macro files are to be put and found. The
  argument passed to this macro is commonly m4."
  https://autotools.io/autoconf/macros.html

Signed-off-by: Rhys Kidd <rhyskidd@gmail.com>

.gitignore

@@ -26,12 +26,7 @@ INSTALL
 install-sh
 .libs/
 libtool
-libtool.m4
 ltmain.sh
-lt~obsolete.m4
-ltoptions.m4
-ltsugar.m4
-ltversion.m4
 Makefile
 Makefile.in
 mdate-sh

Makefile.am

@@ -19,6 +19,9 @@
 #  CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 AUTOMAKE_OPTIONS = foreign
+
+ACLOCAL_AMFLAGS = -I m4
+
 SUBDIRS = src man
 MAINTAINERCLEANFILES = ChangeLog INSTALL
 

configure.ac

@@ -32,6 +32,7 @@ AC_DEFINE_UNQUOTED([NV_DRIVER_DATE],
 
 AC_CONFIG_SRCDIR([Makefile.am])
 AC_CONFIG_HEADERS([config.h])
+AC_CONFIG_MACRO_DIR([m4])
 AC_CONFIG_AUX_DIR(.)
 
 AM_INIT_AUTOMAKE([dist-bzip2])

m4/.gitignore

@@ -0,0 +1,5 @@
+libtool.m4
+lt~obsolete.m4
+ltoptions.m4
+ltsugar.m4
+ltversion.m4