Rollup merge of rust-lang#74291 - regexident:from-docs, r=GuillaumeGomez

Added docs for `From<c_int>` for `ExitStatus`

Partially addresses rust-lang#51430

Author: Manishearth

src/libstd/sys/unix/process/process_fuchsia.rs

@@ -246,6 +246,7 @@ impl ExitStatus {
     }
 }
 
+/// Converts a raw `c_int` to a type-safe `ExitStatus` by wrapping it without copying.
 impl From<c_int> for ExitStatus {
     fn from(a: c_int) -> ExitStatus {
         ExitStatus(a as i64)

src/libstd/sys/unix/process/process_unix.rs

@@ -479,6 +479,7 @@ impl ExitStatus {
     }
 }
 
+/// Converts a raw `c_int` to a type-safe `ExitStatus` by wrapping it without copying.
 impl From<c_int> for ExitStatus {
     fn from(a: c_int) -> ExitStatus {
         ExitStatus(a)

src/libstd/sys/vxworks/process/process_common.rs

@@ -376,6 +376,7 @@ impl ExitStatus {
     }
 }
 
+/// Converts a raw `c_int` to a type-safe `ExitStatus` by wrapping it without copying.
 impl From<c_int> for ExitStatus {
     fn from(a: c_int) -> ExitStatus {
         ExitStatus(a)

src/libstd/sys/windows/process.rs

@@ -378,6 +378,7 @@ impl ExitStatus {
     }
 }
 
+/// Converts a raw `c::DWORD` to a type-safe `ExitStatus` by wrapping it without copying.
 impl From<c::DWORD> for ExitStatus {
     fn from(u: c::DWORD) -> ExitStatus {
         ExitStatus(u)