* use RT_KSERVICE_USING_STDLIB_MEMXXX to replace RT_KSERVICE_USING_STDLIB_MEMCP/MEMSET
* RT_KSERVICE_USING_STDLIB is open by default
* ipc
* Add descriptions for rt_mq_recv and rt_sem_take timeout parameters
* fix parameter name
* enable RT_DEBUG_DEVICE by default and move weak rt_hw_dealy_us in kservice.c
* Updated the Cortex-A of linker scripts for the new version of GCC, Removed C++ global constructor initialization, this method is not used in GCC4.7 and later versions
* remove the register keyword
* rename _rt_scheduler_stack_check as _scheduler_stack_check
* update comments for rt_thread_suspend
* fix comment for rt_container_of
* fixed bug of timer
* remove the executable permission of thread.c
* remove strnlen function
* add NULL check for rt_free and rt_free_align
* suuport perf_counter
* tighten size before check with mem_size_aligned
* Add string information for error
* fix a problem about finsh_set_prompt redefined msh command
* Unify the data type and macro definition of kernel built-in and standard LIBC library
* add macro RT_VERSION_CHECK to implement version check
* fix the style for "rt_hw_us_delay" function
* fix the time slice logic for schedule.c
## Components
* driver
* Detailed classification of devices types
* Update device type definition and command definition
* ioctl add F_SETFL cmd
* fix a problem that eliminate recursion
* fix som compilation warning
* driver/serial_v2
* add support for "termios"
* add hardware flow control support
* fixed bug for RT_SERIAL_TX_BLOCKING model
* add rt_assert for serial_v2
* driver/sensor
* Add blood pressure sensor type
* Add RT_SENSOR_VENDOR_MELEXIS in sensor.h
* Add RT_SENSOR_VENDOR_MELEXIS in sensor_cmd.c
* driver/spi
* remove _spi_bus_device_control
* Fix rt_qspi_send symbol extension BUG
* fix issue report #6008 rt_spi_sendrecv8
* driver/rtc
* Adjust ops function input parameters
* Optimize execution efficiency
* Add get/set timestamp function
* Enhanced date command
* fix the parameter check about "time"
* use gmtime_r to replace gmtime
* driver/alarm
* Fix week alarm bug
* Compact alarm output
* fix a typo
* driver/inputcapture
* add DBG_TAG for rt_inputcapure.c
* driver/hwtimer
* add disable interrupt protection for hwtimer_isr function
* driver/hwcrypto
* Optimize memory usage
* driver/sdio
* Support DDR mode
* modify the address offset problem for sdio read and write
* driver/dac
* fix return value of rt_dac_write function
* add get resolution method
* driver/adc
* add a interface to get sampling resolution
* add finsh voltage conversion command
* implement adc_get_vref
* driver/pwm
* clean the useless code
* add finsh pwm function
* driver/usb
* fix build error
* fix stall bug on control transfers
* add interface to get information about virtual uart connect state
* fix usbhost hid issues
* driver/wlan
* Modify wlan framework
* driver/phy
* fix the PHY_FULL_DUPLEX conflicts
* driver/can
* Add CANFD support and correct typos
* Fix can infinite loop when can driver send error
* driver/hwcrypto
* Correct function return value definition
* driver/pin
* add pin operate command in MSH
* driver/touch
* adjust the header file for touch.h
* libc
* fix c/c++ compilation warnings and errors
* improve sconscript
* fix the sys/select.h problem
* fix that some function cannot be found in unistd.h
* Remove definitions that "posix/io" are not in use
* fix the time bug
* optimize the handle logic on armcc/armclang
* fix the compiler error on iar
* fix dlmodule compile 'SEEK_END' undeclared eror
* the recycle logic about resource of pthread
* fix the function pthread_barrier_init return "EINVAL" if "count" is zero.
* solve the conflicts between libc data types and rtdef data types
* remove strdup from rtthread.h
* Fix clock_gettime for CLOCK_CPUTIME_ID
* solve the libc/timer problem which the os tick can be calculated wrongly because the local variable was not initialized
* implement extension standard C functions
* fix the error return
* modify the complier error in iar
* use atomic operation to protect pthread conditional variable
* memory leak when the value of posix semaphore is zero
* fix a problem that function difftime() compile error in iar environment
* pthread_mutex_destroy can't work
* the risk for function exit() when open pthread support
* supplement the case that exit() haven't been impletement
* try to fix the problem about "fflush" functions in armlibc
* use ```__clang__``` to replace ```__CLANG_ARM```
* solve the compiling error for```_sys_ensure```
* ulog
* Add file backend
* Optimize unnecessary refresh
* sfud
* support NM25Q128EVB, GD25Q32C, SST25VF080B, W25Q32BV, W25X16AV, W25X40CL
* modify the opeated way to handle a situation that flash blocks protected
* keep macros in order
* sal
* add draft for docking winsock
* rearrange sal dependencies
* rename sal.h as sal_low_lvl.h
* at
* use pointer that memory had freed
* implement about "AT server"
* lwip
* Support windows simulator
* add list command
* finish
* fix list_device crash
* Enhance system robustness
* add available memory information for free cmd
* add binary search algorithm
* add new functions to get length of finish cmd
* fal
* support fal api for c++
* modify PKG_USING_FAL to RT_USING_FAL
* utest
* add cpp11 base testcase
* enhance strength about cpp testcase
* add posix testcase frame
* add timeslice test
* ymodem
* move error codes to rym_code to silence warnings
