libunwind: correct 'libuwind' typo

There were several instances of libuwind (missing an "n"), dating to
the initial import of libunwind.


git-svn-id: https://llvm.org/svn/llvm-project/libunwind/trunk@280086 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/src/UnwindLevel1-gcc-ext.c b/src/UnwindLevel1-gcc-ext.c
index edfac30..253e717 100644
--- a/src/UnwindLevel1-gcc-ext.c
+++ b/src/UnwindLevel1-gcc-ext.c
@@ -123,7 +123,7 @@
     _Unwind_Reason_Code result;
 
 #if !_LIBUNWIND_ARM_EHABI
-    // ask libuwind to get next frame (skip over first frame which is
+    // ask libunwind to get next frame (skip over first frame which is
     // _Unwind_Backtrace())
     if (unw_step(&cursor) <= 0) {
       _LIBUNWIND_TRACE_UNWINDING(" _backtrace: ended because cursor reached "