Char: remove many (unnecessary) Char arithmetic operations.

Spurred by #1771. The one I really wanted to get rid of was
Char+Char but that's used by iteration of Char ranges, e.g. here:

https://github.com/JuliaLang/julia/blob/63dd47153097c68643dd3462656a6c74358d04e3/base/intfuncs.jl#L220

In order to get rid of that usage, the way Range iteration works
would need to be changed. Currently it's a bit odd that 'a':'z'
is a Range of Chars, while 'a':1:'z' is a Range of Ints. Maybe
the step type of a Range shouldn't need to be the same as the
start type?

Author: StefanKarpinski

base/char.jl

@@ -42,20 +42,10 @@ promote_rule(::Type{Char}, ::Type{Uint128}) = Uint128
 
 ## character operations & comparisons ##
 
--(x::Char) = -int(x)
-+(x::Char, y::Char) = int(x) + int(y)
--(x::Char, y::Char) = int(x) - int(y)
-*(x::Char, y::Char) = int(x) * int(y)
-
-div(x::Char, y::Char) = div(int(x), int(y))
-fld(x::Char, y::Char) = div(int(x), int(y))
-rem(x::Char, y::Char) = rem(int(x), int(y))
-mod(x::Char, y::Char) = rem(int(x), int(y))
-
-~(x::Char)            = ~uint32(x)
-(&)(x::Char, y::Char) = uint32(x) & uint32(y)
-|(x::Char, y::Char)   = uint32(x) | uint32(y)
-($)(x::Char, y::Char) = uint32(x) $ uint32(y)
+-(x::Char, y::Char) = int(x)-int(y)
++(x::Char, y::Char) = char(int(x)+int(y)) # TODO: delete me
++(x::Char, y::Int ) = char(int(x)+y)
++(x::Int , y::Char) = y+x
 
 <<(x::Char, y::Int32)  = uint32(x) << y
 >>(x::Char, y::Int32)  = uint32(x) >>> y