baremetal: Add KEIL C251 toolchain support
baremetal: Add KEIL C251 toolchain support

This commit adds a basic support of the KEIL toolchain for
the MCS-251 (aka Intel 80251) processors family:

* http://www.keil.com/c251/

Change-Id: I5c3af7ca946ea92eda5989291db1c1d96ce3ecda
Reviewed-by: Christian Kandeler <3aa99dcdd3f0cac61fb81c2a11771c0cc2497607@qt.io>

qtproject/qt-labs-qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qt-labs/qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs,qt-labs/qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs,qt-labs/qbs