Move ntmain.c into libtor-app again

It's needed by main.c

Fixes bug 26662; bug not in any released Tor.

src/core/include.am

@@ -101,6 +101,10 @@ LIBTOR_APP_A_SOURCES = 				\
 	src/feature/stats/geoip.c		\
 	src/feature/stats/rephist.c
 
+if BUILD_NT_SERVICES
+LIBTOR_APP_A_SOURCES += src/app/main/ntmain.c
+endif
+
 #
 # Modules are conditionnally compiled in tor starting here. We add the C files
 # only if the modules has been enabled at configure time. We always add the