Auto merge of #1288 - red75prime:pr-uclibc-arm, r=gnzlbg

Add arm-uclibc definitions

I used `buildroot-2017.05` to build armv7 cross compiler, `uclibc-1.0.24` and `libc-test`. I've executed `libc-test` on armv7-based SoC, using modified `libc-test` to account for the environment. Modified libc-test is not included in this PR because it is too dependent on cross compilation and execution environment.

Author: bors

src/unix/uclibc/arm/align.rs

@@ -0,0 +1,13 @@
+s! {
+    // FIXME this is actually a union
+    #[cfg_attr(target_pointer_width = "32",
+               repr(align(4)))]
+    #[cfg_attr(target_pointer_width = "64",
+               repr(align(8)))]
+    pub struct sem_t {
+        #[cfg(target_pointer_width = "32")]
+        __size: [::c_char; 16],
+        #[cfg(target_pointer_width = "64")]
+        __size: [::c_char; 32],
+    }
+}