mbed OS 5.5.6 release

We are pleased to announce the [mbed OS 5.5.6
release](https://github.com/ARMmbed/mbed-os/releases/tag/mbed-os-5.5.6)
is now available.

This release includes ...

Known Issues

The following list of known issues apply to this release:

Contents

Ports for Upcoming Targets

[4608](ARMmbed#4608)
Support Nuvoton's new target NUMAKER_PFM_M487

[4840](ARMmbed#4840)
Add Support for TOSHIBA TMPM066 board

Fixes and Changes

[4801](ARMmbed#4801)
STM32 CAN: Fix issue with speed function calculation

[4808](ARMmbed#4808)
Make HAL & US tickers idle safe

[4812](ARMmbed#4812)
Use DSPI SDK driver API's in SPI HAL driver

[4832](ARMmbed#4832)
NUC472/M453: Fix several startup and hal bugs

[4842](ARMmbed#4842)
Add call to DAC_Enable as this is no longer done as part

[4849](ARMmbed#4849)
Allow using of malloc() for reserving the Nanostack's heap.

[4850](ARMmbed#4850)
Add list of defines to vscode exporter

[4863](ARMmbed#4863)
Optimize memory usage of wifi scan for REALTEK_RTW8195AM

[4869](ARMmbed#4869)
HAL LPCs SPI: Fix mask bits for SPI clock rate

[4873](ARMmbed#4873)
Fix Cortex-A cache file

[4878](ARMmbed#4878)
STM32 : Separate internal ADC channels with new pinmap

[4392](ARMmbed#4392)
Enhance memap, and configure depth level

[4895](ARMmbed#4895)
Turn on doxygen for DEVICE_* features

[4817](ARMmbed#4817)
Move RTX error handlers into RTX handler file

[4902](ARMmbed#4902)
Using CMSIS/RTX Exclusive access macro

[4923](ARMmbed#4923)
fix export static_files to zip

[4844](ARMmbed#4844)
bd: Add ProfilingBlockDevice for measuring higher-level applications

[4896](ARMmbed#4896)
target BLUEPILL_F103C8 compile fix

[4921](ARMmbed#4921)
Update gcc-arm-embedded PPA in Travis

[4926](ARMmbed#4926)
STM32L053x8: Refactor NUCLEO_L053R8 and DISCO_L053C8 targets

[4831](ARMmbed#4831)
Remove excessive use of printf/scanf in mbed_fdopen/_open

[4922](ARMmbed#4922)
bug fix: xdot clock config

[4935](ARMmbed#4935)
STM32: fix F410RB vectors size

[4940](ARMmbed#4940)
Update mbed-coap to version 4.0.9

[4941](ARMmbed#4941)
Update of MemoryPool.h header file.

You can fetch this release from the [mbed-os
GitHub](https://github.com/ARMmbed/mbed-os) repository,
using the tag "mbed-os-5.5.6".

Please feel free to ask any questions or provide feedback on this
release [on the forum](https://forums.mbed.com/),
or to contact us at [support@mbed.org](mailto:support@mbed.org).