example_util: add ExUtilSetBinaryMode

use it in dwebp when dealing with 'stdout'

Change-Id: I8b8a0b0de9e73731e913ac3c83b5e2b33c693175
cwebp: (windows) open stdout in binary mode

prevents corrupt output. fixes issue #217

Change-Id: If90afb441636144300da66d64f0e7f78505b4060
webpmux: (windows) open stdout in binary mode

prevents corrupt output. related to issue #217

Change-Id: I6f0dac8131127717ba72b0709fb35d421ab41acb
ExUtilReadFromStdin: (windows) open stdin in bin mode

fixes input/decode from stdin in the examples

Change-Id: Ie8052da758a9ef64477501b709408236d258da82