Avoid a branch in getindex(::ASCIIString,::Int)

Should fix #11768.

Author: carnaval

base/ascii.jl

@@ -10,7 +10,7 @@
 ## required core functionality ##
 
 endof(s::ASCIIString) = length(s.data)
-getindex(s::ASCIIString, i::Int) = (x=s.data[i]; x < 0x80 ? Char(x) : '\ufffd')
+getindex(s::ASCIIString, i::Int) = (x=s.data[i]; ifelse(x < 0x80, Char(x), '\ufffd'))
 
 ## overload methods for efficiency ##