FD_ISSET: take a *const fd_set instead of *mut fd_set

FD_ISSET does not modify its fd_set argument, so it may as well take a
const pointer.  AFAICT the only reason to take a *mut pointer is because
the Linux man page documents it that way (though since glibc implements
it as a macro, the constedness is undefined).  But since libc implements
it directly rather than calling a (nonexistent on most platforms) C
function, we're defining the API ourselves.

src/fuchsia/mod.rs

@@ -3158,7 +3158,7 @@ f! {
         return
     }
 
-    pub fn FD_ISSET(fd: ::c_int, set: *mut fd_set) -> bool {
+    pub fn FD_ISSET(fd: ::c_int, set: *const fd_set) -> bool {
         let fd = fd as usize;
         let size = ::mem::size_of_val(&(*set).fds_bits[0]) * 8;
         return ((*set).fds_bits[fd / size] & (1 << (fd % size))) != 0

src/unix/bsd/mod.rs

@@ -541,7 +541,7 @@ f! {
         return
     }
 
-    pub fn FD_ISSET(fd: ::c_int, set: *mut fd_set) -> bool {
+    pub fn FD_ISSET(fd: ::c_int, set: *const fd_set) -> bool {
         let bits = ::mem::size_of_val(&(*set).fds_bits[0]) * 8;
         let fd = fd as usize;
         return ((*set).fds_bits[fd / bits] & (1 << (fd % bits))) != 0

src/unix/haiku/mod.rs

@@ -1295,7 +1295,7 @@ f! {
         return
     }
 
-    pub fn FD_ISSET(fd: ::c_int, set: *mut fd_set) -> bool {
+    pub fn FD_ISSET(fd: ::c_int, set: *const fd_set) -> bool {
         let fd = fd as usize;
         let size = ::mem::size_of_val(&(*set).fds_bits[0]) * 8;
         return ((*set).fds_bits[fd / size] & (1 << (fd % size))) != 0

src/unix/linux_like/mod.rs

@@ -1397,7 +1397,7 @@ f! {
         return
     }
 
-    pub fn FD_ISSET(fd: ::c_int, set: *mut fd_set) -> bool {
+    pub fn FD_ISSET(fd: ::c_int, set: *const fd_set) -> bool {
         let fd = fd as usize;
         let size = ::mem::size_of_val(&(*set).fds_bits[0]) * 8;
         return ((*set).fds_bits[fd / size] & (1 << (fd % size))) != 0

src/unix/newlib/mod.rs

@@ -558,7 +558,7 @@ f! {
         return
     }
 
-    pub fn FD_ISSET(fd: ::c_int, set: *mut fd_set) -> bool {
+    pub fn FD_ISSET(fd: ::c_int, set: *const fd_set) -> bool {
         let bits = ::mem::size_of_val(&(*set).fds_bits[0]) * 8;
         let fd = fd as usize;
         return ((*set).fds_bits[fd / bits] & (1 << (fd % bits))) != 0

src/unix/redox/mod.rs

@@ -898,7 +898,7 @@ f! {
         return
     }
 
-    pub fn FD_ISSET(fd: ::c_int, set: *mut fd_set) -> bool {
+    pub fn FD_ISSET(fd: ::c_int, set: *const fd_set) -> bool {
         let fd = fd as usize;
         let size = ::mem::size_of_val(&(*set).fds_bits[0]) * 8;
         return ((*set).fds_bits[fd / size] & (1 << (fd % size))) != 0

src/unix/solarish/mod.rs

@@ -2171,7 +2171,7 @@ f! {
         return
     }
 
-    pub fn FD_ISSET(fd: ::c_int, set: *mut fd_set) -> bool {
+    pub fn FD_ISSET(fd: ::c_int, set: *const fd_set) -> bool {
         let bits = ::mem::size_of_val(&(*set).fds_bits[0]) * 8;
         let fd = fd as usize;
         return ((*set).fds_bits[fd / bits] & (1 << (fd % bits))) != 0