build: Switch to non-recursive make

Build logic moves from individual Makefile.am's to include files, which
the main src/Makefile.am includes. This avoids having to manage a gigantic
single Makefile.

TODO: Move the rules from the old Makefile.include to where they actually
belong and nuke the old file.

src/Makefile.include

@@ -12,23 +12,18 @@ AM_CPPFLAGS =  $(INCLUDES) \
 AM_CPPFLAGS += $(LEVELDB_CPPFLAGS)
 AM_LDFLAGS = $(PTHREAD_CFLAGS)
 
-LIBBITCOIN_SERVER=$(top_builddir)/src/libbitcoin_server.a
-LIBBITCOIN_WALLET=$(top_builddir)/src/libbitcoin_wallet.a
-LIBBITCOIN_COMMON=$(top_builddir)/src/libbitcoin_common.a
-LIBBITCOIN_CLI=$(top_builddir)/src/libbitcoin_cli.a
-LIBBITCOINQT=$(top_builddir)/src/qt/libbitcoinqt.a
-
-$(LIBBITCOIN):
-	$(MAKE) -C $(top_builddir)/src $(@F)
+LIBBITCOIN_SERVER=libbitcoin_server.a
+LIBBITCOIN_WALLET=libbitcoin_wallet.a
+LIBBITCOIN_COMMON=libbitcoin_common.a
+LIBBITCOIN_CLI=libbitcoin_cli.a
+LIBBITCOINQT=qt/libbitcoinqt.a
 
 if EMBEDDED_LEVELDB
 $(LIBLEVELDB) $(LIBMEMENV):
 	$(MAKE) -C $(top_builddir)/src leveldb/$(@F)
+$(LIBLEVELDB): $(LIBMEMENV)
 endif
 
-$(LIBBITCOINQT):
-	$(MAKE) -C $(top_builddir)/src/qt $(@F)
-
 .mm.o:
 	$(OBJC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) \
 	  $(CPPFLAGS) $(AM_CXXFLAGS) $(QT_INCLUDES) $(CXXFLAGS)  -c -o $@ $<