bump version to 1.2.1

libwebp{,decoder} - 1.2.1
libwebp libtool - 8.2.1
libwebpdecoder libtool - 4.2.1

mux - 1.2.1
libtool - 3.7.0

demux - 1.2.1
libtool - 2.8.0

Bug: webp:521
Change-Id: I098e3e9df698baa275dea85315b9136e565e9971
15 files changed