Support GNAT CE 2020.

  * INSTALL.md: added "gnat-ce-2020" to the RELEASE table.
  * README.md: minor consistency change.
  * common/common.gpr (Compiler_Release): added "gnat-ce-2020".
  * common/gnat-ce-2020/a-tags.adb,
    common/gnat-ce-2020/environment_task.adb,
    common/gnat-ce-2020/s-parame.adb,
    common/gnat-ce-2020/s-parame.ads,
    common/gnat-ce-2020/s-secsta.adb,
    common/gnat-ce-2020/s-secsta.ads,
    common/gnat-ce-2020/s-tarest.adb,
    common/gnat-ce-2020/s-tarest.ads,
    common/gnat-ce-2020/s-taskin.ads: copied from ../gcc8/.
  * common/gnat-ce-2020/a-tags.adb: copied from the gcc-mirror version
      at commit [ead7594]. Commented out the wide string versions of
      the Expanded_Name function.
  * common/gnat-ce-2020/a-tags.ads: likewise.
    (Max_Predef_Prims): this was the required change, now 16, previously
      15.

INSTALL.md

@@ -33,6 +33,7 @@ Values for `RELEASE` are as below:
 | GNAT GPL 2017 | `gnat-gpl-2017` |
 | GNAT CE 2018 | `gcc8` |
 | GNAT CE 2019 | `gcc8` |
+| GNAT CE 2020 | `gnat-ce-2020` |
 
 Build by running
 <tt>make&nbsp;RELEASE=<i>release</i>&nbsp;all</tt> at the top level (or, if you only want one runtime, by <tt>make&nbsp;RELEASE=<i>release</i></tt> in that runtime's subdirectory).

README.md

@@ -1,6 +1,6 @@
 This package includes GNAT Ada Run Time Systems (RTSs) based
 on [FreeRTOS](http://www.freertos.org) and targeted at boards with
-Cortex-M0, M3, -M4, -M4F MCUs
+Cortex-M0, -M3, -M4, -M4F MCUs
 (respectively
 [BBC micro:bit](http://microbit.org),
 [Arduino Due](https://www.arduino.cc), and the STM32F4-series evaluation

common/common.gpr

@@ -18,7 +18,8 @@
 
 abstract project Common is
 
-   type Compiler_Release is ("gcc6", "gnat-gpl-2017", "gcc7", "gcc8");
+   type Compiler_Release is
+     ("gcc6", "gnat-gpl-2017", "gcc7", "gcc8", "gnat-ce-2020");
    Release : Compiler_Release := external ("RELEASE", "gcc8");
 
    type Install_Locally is ("yes", "no");