Added getloadavg for Linux, the BSDs and Solaris.

Sadly Android's bionic lacks this functionality.

Author: raphaelcohn

src/unix/bsd/mod.rs

@@ -342,7 +342,6 @@ f! {
     pub fn WCOREDUMP(status: ::c_int) -> bool {
         (status & 0o200) != 0
     }
-
 }
 
 extern {
@@ -360,6 +359,7 @@ extern {
                       result: *mut *mut passwd) -> ::c_int;
     pub fn getprogname() -> *const ::c_char;
     pub fn setprogname(name: *const ::c_char);
+    pub fn getloadavg(loadavg: *mut ::c_double, nelem: ::c_int) -> ::c_int;
 }
 
 cfg_if! {

src/unix/notbsd/linux/mod.rs

@@ -612,6 +612,7 @@ extern {
                      resource: ::c_int,
                      new_limit: *const ::rlimit64,
                      old_limit: *mut ::rlimit64) -> ::c_int;
+    pub fn getloadavg(loadavg: *mut ::c_double, nelem: ::c_int) -> ::c_int;
 }
 
 cfg_if! {

src/unix/solaris/mod.rs

@@ -903,5 +903,6 @@ extern {
     pub fn uselocale(loc: ::locale_t) -> ::locale_t;
     pub fn getprogname() -> *const ::c_char;
     pub fn setprogname(name: *const ::c_char);
+    pub fn getloadavg(loadavg: *mut ::c_double, nelem: ::c_int) -> ::c_int;
 }