Build: incremental build support, Windows uasync fixes, TUN cross-platform refactoring

- build.sh: added --full flag for full rebuild (autoreconf + configure + make)
- build_direct.sh: incremental compilation (skips unchanged files)
- build_full.bat: new Windows batch for full rebuild
- configure.ac: fixed Windows detection using AC_COMPILE_IFELSE
- lib/u_async.c/h: Windows wakeup socket support, uasync_post for thread-safe callbacks
- src/tun_if.c/h: cross-platform TUN refactoring, Windows read thread support
- src/tun_windows.c: Windows TUN implementation improvements
- src/control_server.c: removed premature return statement
- src/routing.c: include ordering fix
- src/utun.c: windows compat includes
- Deleted obsolete net_emulator/Makefile and tinycrypt/Makefile

tinycrypt/Makefile

@@ -1,21 +0,0 @@
-################################################################################
-#
-#      Copyright (C) 2017 by Intel Corporation, All Rights Reserved.
-#
-# 								           Global Makefile. 
-#	  		See lib/Makefile and tests/Makefile for further configuration.
-#
-################################################################################
-include config.mk
-
-all:
-	$(MAKE) -C lib
-ifeq ($(ENABLE_TESTS),true)
-	$(MAKE) -C tests
-endif
-
-clean:
-	$(MAKE) -C lib clean
-	$(MAKE) -C tests clean
-	$(RM) *~
-