Add Jansson vendor library.

vendor/Jansson/scripts/clang-format-check

@@ -0,0 +1,27 @@
+#!/bin/bash
+
+CLANG_FORMAT=${CLANG_FORMAT:-clang-format}
+CLANG_FORMAT_VERSION=${CLANG_FORMAT_VERSION:-}
+
+if ! type $CLANG_FORMAT >/dev/null || \
+        ! $CLANG_FORMAT --version | grep -q "version ${CLANG_FORMAT_VERSION}"; then
+    # If running tests, mark this test as skipped.
+    exit 77
+fi
+
+errors=0
+paths=$(git ls-files | grep '\.[ch]$')
+for path in $paths; do
+    in=$(cat $path)
+    out=$($CLANG_FORMAT $path)
+
+    if [ "$in" != "$out" ]; then
+        diff -u -L $path -L "$path.formatted" $path - <<<$out
+        errors=1
+    fi
+done
+
+if [ $errors -ne 0 ]; then
+    echo "Formatting errors detected, run ./scripts/clang-format to fix!"
+    exit 1
+fi