The Linux target's sys/lock.h provided no-op inline stubs, which was
safe only under the assumption of single-threaded execution. With the
new FreeRTOS Linux simulator using soft preemption, an outgoing task
can still run concurrently with the incoming task until it reaches a
yield point, making no-op locks unsafe.
Replace the no-op implementation with real pthread mutexes:
- Change _lock_t from `typedef int` to `typedef void *` (pointer to a
heap-allocated pthread_mutex_t).
- Implement all _lock_* functions in a new lock.c, supporting both
normal and recursive mutexes.
- Zero-initialized locks are lazily created on first acquire using
double-checked locking, preserving newlib/esp_libc semantics.
- Add lock.c unconditionally to the linux component sources and link
pthread.
* Users can now use libbsd string.h and sys/cdefs.h functionality
(e.g., strlcpy, containerof) on Linux by just including
string.h or sys/cdefs.h. In other words, the includes are the same
on the Linux target as well as on chips targets (ESP32, etc.).
* libbsd linking is done by the linux component (belongs to common
components) now instead of handling it separately in each component
Some files that should have their copyrights checked are still placed on the
copyright ignore list.
- These entries have been tidied up
- Copyrights of those files have been updated.
linux/lwip: Wrap some IO posix functions
* to workaourd the FreeRTOS EINTR issue (when building without lwip)
* to correctly choose the sub-system based on fd (when building with
lwip) -- passing control to either linux/system or to lwip
This commit also addapts tapio-if to provide DHCP client by default and
configurable settings for static IP
