Close an I/O stream. This implements Perl "close" in perlfunc.

gv is the glob associated with the stream.

is_explict is true if this is an explicit close of the stream; false if it is part of another operation, such as closing a pipe (which involves implicitly closing both ends).

Returns true if successful; otherwise returns false and sets errno to indicate the cause.

The C library chsize(3) if available, or a Perl implementation of it.

Function called by do_readline to spawn a glob (or do the glob inside perl on VMS). This code used to be inline, but now perl uses File::Glob this glob starter is only used by miniperl during the build process, or when PERL_EXTERNAL_GLOB is defined. Moving it away shrinks pp_hot.c; shrinking pp_hot.c helps speed perl up.