h264parse: wait for resolution to be known before pushing

Submitted by Vincent Penquerc'h @vincent

Link to original bug (#728324)

Description

Created attachment 274433
wait to get resolution before pushing buffers

This is something done a few years back for 0.10, and which may be useful to upstream.

Patch 274433, "wait to get resolution before pushing buffers":
0002-h264parse-wait-to-get-resolution-before-pushing-buff.patch