Remove explicit inclusion of our m4 files first. It was interesting as a test,

but it breaks aclocal execution on some systems, with the following error:

Can't locate object method "rel2abs" via package "File::Spec" at /usr/local/bin/aclocal line 256.

configure.ac

@@ -1,13 +1,5 @@
 AC_PREREQ(2.57)
 
-dnl Explicitly include our m4 files first. Without these explicit inclusions
-dnl aclocal will actually find and include them automatically, but before it
-dnl does it might fully scan all other system installed m4 files. Doing this
-dnl explicit inclusion also allows us to override definitions of macros done
-dnl elsewhere in other packages with the ones done in our included files.
-m4_include([m4/reentrant.m4])
-m4_include([acinclude.m4])
-
 dnl Version not hardcoded here. Fetched later from ares_version.h
 AC_INIT([c-ares], [-],
   [c-ares mailing list => http://cool.haxx.se/mailman/listinfo/c-ares])