Fix libm underlinking.
Gentoo-Bug: https://bugs.gentoo.org/show_bug.cgi?id=508132

--- timemachine-0.3.3/configure.ac
+++ timemachine-0.3.3/configure.ac
@@ -1,6 +1,6 @@
 dnl Process this file with autoconf to produce a configure script.
 
-AC_INIT(configure.in)
+AC_INIT(configure.ac)
 AM_INIT_AUTOMAKE(timemachine, 0.3.3)
 AM_CONFIG_HEADER(config.h)
 AM_MAINTAINER_MODE
@@ -10,6 +10,11 @@
 AM_PROG_CC_STDC
 AC_HEADER_STDC
 
+dnl Check for libm for log10()
+AC_SEARCH_LIBS([log10], [m], [], [
+	AC_MSG_ERROR([unable to find the log10() function])
+])
+
 PKG_CHECK_MODULES(GTK, [gtk+-2.0 >= 2.0.0])
 PKG_CHECK_MODULES(JACK, [jack >= 0.80.0])
 PKG_CHECK_MODULES(LIBLO, liblo >= 0.24, LO_FOUND="yes", LO_FOUND="no")