Fixed typo
Added/updated license headers.
Optionally disable SSE optimizations.

Added configure option --disable-sse to compile without SSE optimizations even if compiler supports it. This is required for example when compiling with Emscripten.
Merge remote-tracking branch 'remotes/jojo/configure_disable_features'
remove duplicate code
better image integrity tracking, skip without full decoder reset
store NAL header as image meta-information
test stream skipping
rename and cleanup image initialization function