Get ourselves some clang-format and apply it

Add clang-format and apply it to all *.cpp *.h files under jni/

Test: make
Change-Id: I3fe84eb3a65b73d8b38bb9bd52c07945835ede70
diff --git a/PREUPLOAD.cfg b/PREUPLOAD.cfg
new file mode 100644
index 0000000..c8dbf77
--- /dev/null
+++ b/PREUPLOAD.cfg
@@ -0,0 +1,5 @@
+[Builtin Hooks]
+clang_format = true
+
+[Builtin Hooks Options]
+clang_format = --commit ${PREUPLOAD_COMMIT} --style file --extensions c,h,cc,cpp