samples: add Terra samples

source: https://github.com/zdevito/terra/tree/master/tests

samples/Terra/pthreads.t

@@ -0,0 +1,47 @@
+local ffi = require("ffi")
+if ffi.os == "Windows" then
+  return
+end
+
+C = terralib.includecstring [[
+#include <pthread.h>
+#include <stdio.h>
+]]
+
+acc = global(int[4])
+
+terra forkedFn(args : &opaque) : &opaque
+  var threadid = @[&int](args)
+  C.printf("threadid %d\n",threadid)
+  acc[threadid] = threadid
+  return nil
+end
+
+terra foo()
+  var thread0 : C.pthread_t
+  var thread1 : C.pthread_t
+  var thread2 : C.pthread_t
+  var thread3 : C.pthread_t
+
+  acc[0]=-42
+  acc[1]=-42
+  acc[2]=-42
+  acc[3]=-42
+
+  var args = arrayof(int,0,1,2,3)
+
+  C.pthread_create(&thread0,nil,forkedFn,&args[0])
+  C.pthread_create(&thread1,nil,forkedFn,&args[1])
+  C.pthread_create(&thread2,nil,forkedFn,&args[2])
+  C.pthread_create(&thread3,nil,forkedFn,&args[3])
+
+  C.pthread_join(thread0,nil)
+  C.pthread_join(thread1,nil)
+  C.pthread_join(thread2,nil)
+  C.pthread_join(thread3,nil)
+
+  return acc[0]+acc[1]+acc[2]+acc[3]
+end
+
+local test = require("test")
+test.eq(foo(),0+1+2+3)