auto merge of #17896 : mahkoh/rust/intmax, r=alexcrichton

Closes #17075

I don't know if this is correct. The easiest way to find out is to run the following program on all targets but I can't do it myself.
```c
#include <stdint.h>
#include <stdio.h>

int main(void)
{
	if (sizeof(intmax_t) != 8) {
		puts("ERROR");
		return 1;
	}
}
```

src/liblibc/lib.rs

@@ -103,6 +103,7 @@ pub use types::os::arch::c95::{c_ushort, clock_t, ptrdiff_t, c_schar};
 pub use types::os::arch::c95::{size_t, time_t, suseconds_t};
 pub use types::os::arch::c99::{c_longlong, c_ulonglong};
 pub use types::os::arch::c99::{intptr_t, uintptr_t};
+pub use types::os::arch::c99::{intmax_t, uintmax_t};
 pub use types::os::arch::posix88::{dev_t, ino_t, mode_t};
 pub use types::os::arch::posix88::{off_t, pid_t, ssize_t};
 
@@ -533,6 +534,8 @@ pub mod types {
                 pub type c_ulonglong = u64;
                 pub type intptr_t = i32;
                 pub type uintptr_t = u32;
+                pub type intmax_t = i64;
+                pub type uintmax_t = u64;
             }
             #[cfg(any(target_arch = "x86",
                       target_arch = "mips",
@@ -740,6 +743,8 @@ pub mod types {
                 pub type c_ulonglong = u64;
                 pub type intptr_t = i64;
                 pub type uintptr_t = u64;
+                pub type intmax_t = i64;
+                pub type uintmax_t = u64;
             }
             pub mod posix88 {
                 pub type off_t = i64;
@@ -973,6 +978,8 @@ pub mod types {
                 pub type c_ulonglong = u64;
                 pub type intptr_t = i64;
                 pub type uintptr_t = u64;
+                pub type intmax_t = i64;
+                pub type uintmax_t = u64;
             }
             pub mod posix88 {
                 pub type off_t = i64;
@@ -1186,6 +1193,8 @@ pub mod types {
                 pub type c_ulonglong = u64;
                 pub type intptr_t = i64;
                 pub type uintptr_t = u64;
+                pub type intmax_t = i64;
+                pub type uintmax_t = u64;
             }
             pub mod posix88 {
                 pub type off_t = i64;
@@ -1426,6 +1435,9 @@ pub mod types {
                 pub type uintptr_t = u32;
                 #[cfg(target_arch = "x86_64")]
                 pub type uintptr_t = u64;
+
+                pub type intmax_t = i64;
+                pub type uintmax_t = u64;
             }
 
             pub mod posix88 {
@@ -1815,6 +1827,8 @@ pub mod types {
                 pub type c_ulonglong = u64;
                 pub type intptr_t = i32;
                 pub type uintptr_t = u32;
+                pub type intmax_t = i64;
+                pub type uintmax_t = u64;
             }
             pub mod posix88 {
                 pub type off_t = i64;
@@ -1916,6 +1930,8 @@ pub mod types {
                 pub type c_ulonglong = u64;
                 pub type intptr_t = i64;
                 pub type uintptr_t = u64;
+                pub type intmax_t = i64;
+                pub type uintmax_t = u64;
             }
             pub mod posix88 {
                 pub type off_t = i64;