[PATCH 05/11] dtc: clean up grow_data_for()

[Milton Miller <miltonm@bga.com>]

Change the grow_data_for function to copy struct data and
modifiy the fields it is updating instead of storing all
fields individually to a stack allocated struct.

This reduces maintence for future enhancements as now all
instances of struct data are created by modifying a copy
of an existing struct data or directly copying empty_data.

Signed-off-by: Milton Miller <miltonm@bga.com>
--- 
It took me a bit of time to find the source of the
uninitialized pointer that was causing my changes
to segfault.

diff --git a/data.c b/data.c
index 5d7db17..3d68792 100644
--- a/data.c
+++ b/data.c
@@ -57,6 +57,8 @@ struct data data_grow_for(struct data d,
 	if (xlen == 0)
 		return d;
 
+	nd = d;
+
 	newsize = xlen;
 
 	while ((d.len + xlen) > newsize)
@@ -64,8 +66,6 @@ struct data data_grow_for(struct data d,
 
 	nd.asize = newsize;
 	nd.val = xrealloc(d.val, newsize);
-	nd.len = d.len;
-	nd.refs = d.refs;
 
 	assert(nd.asize >= (d.len + xlen));