vxworks: ensure kernel symbols are not exposed

Deprecate uses of kernel symbols. Rust has support only for RTP
programs.

Removep polyfill routines. They were stubs. They returned error values.
They don't exist in VxWorks.

Author: dybucc

src/new/vxworks/mod.rs

@@ -1,4 +1,7 @@
 //! VxWorks libc.
+//!
+//! VxWorks allows compiling different types of programs. The `libc` crate only
+//! supports RTPs. Refer to the RTP definitions in case of discrepancy.
 // FIXME(vxworks): link to headers needed.
 
 pub(crate) mod unistd;

src/vxworks/mod.rs

@@ -58,7 +58,12 @@ pub type pthread_key_t = c_ulong;
 
 // From b_off_t.h
 pub type off_t = c_longlong;
-pub type off64_t = off_t;
+
+#[deprecated(
+    since = "0.2.187",
+    note = "Kernel mode definitions are unsupported. Use `off_t` instead."
+)]
+pub type off64_t = c_longlong;
 
 // From b_BOOL.h
 pub type BOOL = c_int;
@@ -2414,14 +2419,6 @@ safe_f! {
     }
 }
 
-pub unsafe fn pread(_fd: c_int, _buf: *mut c_void, _count: size_t, _offset: off64_t) -> ssize_t {
-    -1
-}
-
-pub unsafe fn pwrite(_fd: c_int, _buf: *const c_void, _count: size_t, _offset: off64_t) -> ssize_t {
-    -1
-}
-
 pub unsafe fn posix_memalign(memptr: *mut *mut c_void, align: size_t, size: size_t) -> c_int {
     // check to see if align is a power of 2 and if align is a multiple
     //  of sizeof(void *)