Kill struct IOVEC

struct iovec is used as an interface to system (posix) api's. As such,
we shouldn't be using it in os-independent code, and we shouldn't be
defining our own iovec replacements.

Fortunately, its usage was not very widespread, so the removal was very
easy -- I simply moved a couple declarations into os-specific code.

llvm-svn: 319536
diff --git a/lldb/source/Plugins/Process/Linux/NativeProcessLinux.cpp b/lldb/source/Plugins/Process/Linux/NativeProcessLinux.cpp
index a10bd86..decd3af 100644
--- a/lldb/source/Plugins/Process/Linux/NativeProcessLinux.cpp
+++ b/lldb/source/Plugins/Process/Linux/NativeProcessLinux.cpp
@@ -177,7 +177,7 @@
     break;
   }
   case PTRACE_SETREGSET: {
-    // Extract iov_base from data, which is a pointer to the struct IOVEC
+    // Extract iov_base from data, which is a pointer to the struct iovec
     DisplayBytes(buf, *(void **)data, data_size);
     LLDB_LOGV(log, "PTRACE_SETREGSET {0}", buf.GetData());
     break;