examples/nanoxterm: add Nano-X terminal emulator example

* Port the nxterm demo from Microwindows
* Starts the Nano-X server as a separate task before connecting
* Runs an NSH shell instance on a pseudo terminal in the forked child
  instead of exec /bin/sh (no filesystem binaries in flat builds)

Signed-off-by: Acfboy <AcfboyU@outlook.com>

examples/nanoxterm/Kconfig

@@ -0,0 +1,29 @@
+config EXAMPLES_NANOXTERM
+	tristate "Nano-X terminal emulator example"
+	default n
+	depends on MICROWINDOWS_NANOX && PSEUDOTERM && ARCH_HAVE_FORK
+	---help---
+		Enable the Nano-X terminal emulator example application.  It is
+		a port of the nxterm demo from Microwindows.  It starts the
+		Nano-X server, connects to it and creates a
+		terminal window that runs an NSH shell instance on a pseudo
+		terminal.
+
+if EXAMPLES_NANOXTERM
+
+config EXAMPLES_NANOXTERM_PROGNAME
+	string "Program name"
+	default "nanoxterm"
+	---help---
+		This is the name of the program that will be used when the NSH ELF
+		program is installed.
+
+config EXAMPLES_NANOXTERM_PRIORITY
+	int "Nano-X terminal emulator task priority"
+	default 100
+
+config EXAMPLES_NANOXTERM_STACKSIZE
+	int "Nano-X terminal emulator stack size"
+	default 16384
+
+endif

examples/nanoxterm/Make.defs

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+############################################################################
+# apps/examples/nanoxterm/Make.defs
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.  The
+# ASF licenses this file to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance with the
+# License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+# License for the specific language governing permissions and limitations
+# under the License.
+#
+############################################################################
+
+ifneq ($(CONFIG_EXAMPLES_NANOXTERM),)
+CONFIGURED_APPS += $(APPDIR)/examples/nanoxterm
+endif

examples/nanoxterm/Makefile

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+############################################################################
+# apps/examples/nanoxterm/Makefile
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.  The
+# ASF licenses this file to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance with the
+# License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+# License for the specific language governing permissions and limitations
+# under the License.
+#
+############################################################################
+
+include $(APPDIR)/Make.defs
+
+PROGNAME  = $(CONFIG_EXAMPLES_NANOXTERM_PROGNAME)
+PRIORITY  = $(CONFIG_EXAMPLES_NANOXTERM_PRIORITY)
+STACKSIZE = $(CONFIG_EXAMPLES_NANOXTERM_STACKSIZE)
+MODULE    = $(CONFIG_EXAMPLES_NANOXTERM)
+
+# Port of the upstream nxterm demo (src/demos/nanox/nxterm.c).  On NuttX
+# the pty child runs an NSH instance (nsh_consolemain) instead of exec'ing
+# /bin/sh, since flat builds have no filesystem binaries.
+MAINSRC = nxterm.c
+CFLAGS += -Wno-undef
+
+
+include $(APPDIR)/Application.mk