Incremeted release candidate to 2.1.0-rc4

git-svn-id: file:///home/quintiliani/svncopy/nmxptool/trunk@1403 3cd66e75-5955-46cb-a940-c26e5fc5497d

configure.in

@@ -13,7 +13,7 @@ m4_define([major_version], [2])
 m4_define([minor_version], [1])
 m4_define([micro_version], [0])
 # Comment build_version for stable release
-m4_define([build_version], [rc3])
+m4_define([build_version], [rc4])
 
 m4_ifdef([build_version], [
 	  m4_define([version],