Allow strings in DefaultContext's api_buffer

[visr]

In the common case, dump_to_buffer creates a Vector{Any} buffer:

Clang.jl/src/expr_unit.jl

Line 66 in c2c0ea3

buffer = []

Which is then used to mix Expr and String, using the latter for comments in print_buffer:

Clang.jl/src/expr_unit.jl

Line 27 in c2c0ea3

state = (isa(e, AbstractString) ? :string :

Unfortunately I cannot use this in api_buffer since it is set to Vector{Expr} only. With this tweak, I can let my rewriter function insert docstrings that will look the way I want. I know I can put docstr + function together in an expression, but that prints ugly with the at-doc macro.

If you prefer I can also just make it Vector{Union{Expr, String}}

[Gnimuc]

Thanks. I think Vector{Any} is better since there is no reason to constrain its type.