read-stream-content-into-string element-type fix
Default the element type of the string being created from the element type of the stream being read.
This has two advantages: it will make things work for implementations
which have a mode where the default string element type is a subtype
character, and it will also mean that if the stream's element type
is a subtype of
character you may get thinner strings.
In addition the element type of the buffer is also made to be the same as the element type of the string.
Closes #24 (closed)