build: Add coverage.py tool that introduces --with-coverage configure option

Change-Id: I1c6eeb71c734ef8b37e06cc5ac3d0b40aef492da
diff --git a/wscript b/wscript
index 7f33a8e..f0b04ac 100644
--- a/wscript
+++ b/wscript
@@ -5,7 +5,7 @@
 
 def options(opt):
     opt.load('compiler_cxx')
-    opt.load('boost doxygen', tooldir=['.waf-tools'])
+    opt.load('boost doxygen coverage', tooldir=['.waf-tools'])
 
     nfdopt = opt.add_option_group('NFD Options')
     nfdopt.add_option('--debug',action='store_true',default=False,dest='debug',help='''Compile library debugging mode without all optimizations (-O0)''')
@@ -58,6 +58,8 @@
     
     conf.check_cxx(lib='rt', uselib_store='RT', define_name='HAVE_RT', mandatory=False)
 
+    conf.load('coverage')
+
     conf.write_config_header('daemon/config.hpp')
 
 def build(bld):