Check for vpx library

Change-Id: I63018f0f7b53f1a559b8c60ed4c6fada9fd6c8fb
vp8parse: Add private data structure

Change-Id: I8d1e9ed55afed29d4e2f4510a2f745379819d87c
vp8parse: Add start function to initialize variables before proccess starts

Change-Id: Ica9a0a7397f3c1fe3df247119c81c3b19a7675aa
vp8parse: Add passthrough functionality

Change-Id: I6548d016e04539d34944b62e4342268ebe40fbf1
vp8parse: Detect frame dimensions using vpx parse functionality

Change-Id: Ib7fabee93df4fd5a0ec731e693a121d30c2d54d1
vp8parse: Detect framerate and set it to src caps

Change-Id: I2cb0144644ee672924899891a136571eaa2bb3b8
vp8parse: Update timing information if it is available

Change-Id: Ief5127e0aaf8a17b95181bf79a1d1561ed63af9d
vp8parse: Indicate framerate to parent class

Change-Id: I1ba9bb166f6e43e9da3400917e3f8f04cc6d40c9
vp8parse: Increase rank to allow agnosticbin to use vp8parse

Change-Id: I257dcbaefe59111ce37ec39a8d30fc24b01aeaa6