Rename ismatch to occursin; fix 0.7 depwarns

[jmkuhn]

ismatch has been renamed to occursin in Julia Base.
JuliaLang/julia#24673
JuliaLang/julia#26283

To accommodate this in Glob, for Julia 0.6 allow
either ismatch or occursin to be used.

julia> using Glob

julia> using Compat

julia> ismatch(fn"AB*AB*AB", "ABXABXAB")
true

julia> occursin(fn"AB*AB*AB", "ABXABXAB")
true

With the current 0.7 nightly, ismatch produces a deprecation warning.

julia> using Glob

julia> ismatch(fn"AB*AB*AB", "ABXABXAB")
┌ Warning: `ismatch(fn::FilenameMatch, s::AbstractString)` is deprecated, use `occursin(fn, s)` instead.
│   caller = top-level scope
└ @ Core :0
true

julia> occursin(fn"AB*AB*AB", "ABXABXAB")
true

I'm not sure my updates to the iterator are the best way to do this. If you have any suggestions, let me know.

[coveralls]

Coverage increased (+1.1%) to 91.866% when pulling d1a4a75 on jmkuhn:0.7 into 8ca3670 on vtjnash:master.

[coveralls]

Coverage increased (+2.3%) to 93.056% when pulling 442c15e on jmkuhn:0.7 into 8ca3670 on vtjnash:master.

[vtjnash]

Thanks! It's looking good. I've left some comments on the best way to update these.

[vtjnash]

Use the following pattern here:

     patnext = iterate(pattern, mi)
     if patnext === nothing
        match = false # string characters left to match, but no pattern left
     else
          mc, mi = patnext

[vtjnash]

Rewrite this as:

     while true # allow trailing *'s
         patnext = iterate(pattern, mi)
         patnext === nothing && break
         mc, mi = patnext
         mc == '*' || return false # pattern characters left to match, but no string left
     end

[vtjnash]

Can we update this method to compute this at the top:

i = firstindex(s)
while true
    matchnext = iterate(s, i)
    matchnext === nothing && break
...
    c, _ = matchnext # peek-ahead
...
    c, i = matchnext
...
end

[vtjnash]

    if (!noescape) & (mc == '\\') # escape the next character after backslash, unless it is the last character
        patnext = iterate(pattern, mi)
        if patnext !== nothing
            mc, mi = patnext
        end
    end

[vtjnash]

    c, i = something(iterate(s, starmatch)) # starmatch is strictly <= i, so it is known that it must be a valid index

[vtjnash]

wrap in something() (like above)

[vtjnash]

wrap in something() (like above)

[vtjnash]

like you did above, use:

next = iterate(pat, i)
if next === nothing
    return (i0, false, c=='[')
end
mc, j = next

[vtjnash]

similar to above, use:

while true
    next = iterate(pat, i)
    next === nothing && break
    mc, i = next
...
end

[vtjnash]

similarly for all of these lines, use the assignment to the temporary next variable pattern for these that follow here

[jmkuhn]

Thanks for the thorough review. The iterator code looks much better now.