Add .gitignore for autotools files

This makes development work less error prone when committing.

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>

.gitignore

@@ -0,0 +1,13 @@
+Makefile.in
+/autom4te.cache
+/aclocal.m4
+/compile
+/configure
+/depcomp
+/install-sh
+/missing
+/stamp-h1
+/config.guess
+/config.h.in
+/config.sub
+/ltmain.sh