cp: add support for --parents and long option synonyms of short opts

By Ian Wienand (ianw AT vmware.com)

function                                             old     new   delta
cp_main                                              257     369    +112
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/0 up/down: 112/0)             Total: 112 bytes
   text    data     bss     dec     hex filename
 823000     458    6948  830406   cabc6 busybox_old
 823283     458    6948  830689   cace1 busybox_unstripped

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/testsuite/cp/cp-parents b/testsuite/cp/cp-parents
new file mode 100644
index 0000000..a721cea
--- /dev/null
+++ b/testsuite/cp/cp-parents
@@ -0,0 +1,5 @@
+mkdir -p foo/bar/baz
+touch foo/bar/baz/file
+mkdir dir
+busybox cp --parents foo/bar/baz/file dir
+test -f dir/foo/bar/baz/file