add map and filter for inline strings #5
Description
The problem is that current generic implementations for AbstractString fall back to String, so e.g. we have:
julia> x = InlineString("abc")
"abc"
julia> typeof(x)
InlineString3
julia> uppercase(x)
"ABC"
julia> typeof(uppercase(x))
String
julia> filter(==('a'), x)
"a"
julia> typeof(filter(==('a'), x))
String