Add word boundaries to Vim search patterns

This shouldn't be necessary except that the semantic highlighting
performed by luainspect.vim conflicts with the dynamic highlighting
created by my easytags.vim plug-in and this exposes a strange
highlighting bug, where for example in the following:

    local function foobar() end

The 'f' of 'foobar' is highlighted as luaFuncTag while 'oobar' is
highlighted as luaInspectLocalUnused. Note that this bug doesn't
seem to surface unless the two plugins both want to highlight
the same variable...

luainspect.vim

@@ -63,7 +63,7 @@ EOF
   " Highlight variables in buffer based on positions.
   for fields in split(listing, "\n")
     let [type, lnum, start, end] = split(fields)
-    let command = 'syntax match %s /\%%%il\%%>%ic.\+\%%<%ic/'
+    let command = 'syntax match %s /\%%%il\%%>%ic\<\w\+\>\%%<%ic/'
     execute printf(command, type, lnum, start - 1, end + 2)
   endfor
 endfunction