For ape, we never enabled warnings in cflags.
Turning it on brings up a lot of warnings. Most are noise,
but a few caught unused variables and trunctaions of pointers.
to smaller integers (int, long).
A few warnings remain.
remove envname length limitation in _envsetup()
by using allocated buffer and use /env instead of #e
use /proc and getpid() instead of #p and #c in
readprocfdinit()
fix buffer overflow in execlp(), check if name
of failed exec starts with / . or is \0
make sure not to close our own filedescriptors
for FD_CLOEXEC in execve(), fix wrong length
check for flushing buffer to /env/_fdinfo.
fix error handling cases. copy the enviroment
before decoding \1 to \0 because the strings in
environ[] array might not be writable.
remove bogus close if we fail to open ppid file
in getppid() and use /dev/ppid instead of #c/ppid
