build: require automake version at least 1.10

Previous versions don't define MKDIR_P and some other useful things. Since
automake 1.10 was released 2+ years ago this requirment is reasonable.

configure.ac

@@ -25,7 +25,7 @@ AC_PREREQ(2.59)
 AC_CONFIG_SRCDIR(src/integer/gcd/cl_I_gcd.cc)
 AC_CONFIG_AUX_DIR([autoconf])
 AC_CONFIG_HEADERS(autoconf/cl_config.h include/cln/config.h include/cln/host_cpu.h include/cln/version.h src/base/cl_base_config.h src/base/cl_gmpconfig.h src/timing/cl_t_config.h)
-AM_INIT_AUTOMAKE([foreign 1.8 dist-bzip2])
+AM_INIT_AUTOMAKE([foreign 1.10 dist-bzip2])
 AH_TOP([#ifndef _CL_CONFIG_H])
 AH_TOP([#define _CL_CONFIG_H])
 AH_TOP([#include "cln/host_cpu.h"])