adds base64 decoding (fixes #5656)
improves efficiency, moves alias to deprecated.jl, removes trailing whitespace
Merge remote-tracking branch 'upstream/master' into base64_decode_#5656

Conflicts:
	base/deprecated.jl
update old names in other files
avoid creating new array for each 4 byte block
Merge remote-tracking branch 'upstream/master' into base64_decode_#5656

Conflicts:
	NEWS.md
	base/deprecated.jl
Merge pull request #9157 from amartgon/base64_decode_#5656

adds base64 decoding (fixes #5656)