54566: zpty: fix some issues

checkptycmd would sign extend a 0xff byte to -1, causing the byte to be
dropped, read into an unsigned char instead

the "last despairing effort" code read directly into the int, which
would probably not work on big endian. read into a temporary unsigned
char instead

the FIONREAD path used a totally undeclared variable "val", declare it,
and also initialize pollret to -1 for this path

the USE_CYGWIN_FIX path error message would always report -1 as the fd
it was unable to duplicate, report the original fd instead

initial read before the main loop in ptyread forgot to metafy the byte

avoid calling malloc with 0 length as this may be misinterpreted as oom

don't try to open sfd if opening mfd failed

0 files changed, 0 insertions, 0 deletions