Move macro.h to shared directory

It's not really related to libkmod, so move it to a directory in which
we keep common stuff.
diff --git a/Makefile.am b/Makefile.am
index eb63073..8724de5 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -14,6 +14,7 @@
 AM_CPPFLAGS = \
 	-include $(top_builddir)/config.h \
 	-I$(top_srcdir)/libkmod \
+	-I$(top_srcdir) \
 	-DSYSCONFDIR=\""$(sysconfdir)"\" \
 	-DLIBEXECDIR=\""$(libexecdir)"\" \
 	${zlib_CFLAGS}
@@ -53,9 +54,9 @@
 lib_LTLIBRARIES = libkmod/libkmod.la
 
 libkmod_libkmod_la_SOURCES =\
+	shared/macro.h \
 	libkmod/libkmod.h \
 	libkmod/libkmod-internal.h \
-	libkmod/macro.h \
 	libkmod/missing.h \
 	libkmod/libkmod.c \
 	libkmod/libkmod-list.c \