tools: Added astyle,pylint and xmllint checks

Added small bash scripts to run astyle, pylint and xmllint
checks over the kernel source. These style checks were ported
from the old Make build system.

tools/kernel_pylint.sh

@@ -0,0 +1,26 @@
+#!/bin/bash
+
+#
+# Copyright 2018, Data61
+# Commonwealth Scientific and Industrial Research Organisation (CSIRO)
+# ABN 41 687 119 230.
+#
+# This software may be distributed and modified according to the terms of
+# the BSD 2-Clause license. Note that NO WARRANTY is provided.
+# See "LICENSE_BSD2.txt" for details.
+#
+# @TAG(DATA61_BSD)
+#
+
+python_sources=$(find ../tools ../manual/tools ../libsel4/tools -name '*.py')
+if [[ -z $python_sources ]]; then
+    echo "Unable to find python source files"
+    exit 1
+fi
+pylintrc=$(find . -name 'pylintrc')
+if [[ -z $pylintrc ]]; then
+    echo "Unable to find pylintrc"
+    exit 1
+fi
+
+pylint --errors-only --rcfile=${pylintrc} ${python_sources}