Build system: add build-system related info

Add a few information on the build system. These information
will help to run bootstrap correctly.

Makefile.am

@@ -1,5 +1,6 @@
 ## Process this file with automake to generate Makefile.in
 AUTOMAKE_OPTIONS        = foreign nostdinc
+ACLOCAL_AMFLAGS         = -I m4
 
 AM_CPPFLAGS             = -I. -I$(top_srcdir)
 AM_LD                   = $(CC)

configure.ac

@@ -10,6 +10,7 @@ AC_INIT([klish],
         [serj.kalichev at gmail dot com])
 
 AC_CONFIG_AUX_DIR(aux_scripts)
+AC_CONFIG_MACRO_DIR([m4])
 
 # Check for system extensions (_POSIX_THREAD_SEMANTICS for Solaris)
 AC_USE_SYSTEM_EXTENSIONS