title: print xtable gsub locale problems
body: <p>I have a data table where some fields are copied and pasted from word documents. When I attempt to output xtable prints from RMarkdown, it get this error:</p>
  
  <pre><code>Error in gsub("&amp;", "&amp;amp;", result, fixed = TRUE) : 
    input string 3 is invalid in this locale
  Calls: &lt;Anonymous&gt; ... eval -&gt; eval -&gt; print -&gt; print.xtable -&gt; sanitize -&gt; gsub
  Execution halted
  </code></pre>
  
  <p>Here's a reproducible example. I called this dataframe test4:</p>
  
  <pre><code>library(xtable)
  test4 &lt;- structure(list(Record.ID = 81, Record.Type = "Type1", Short.Description = "specify 2-8\xb0C storage location",Record.State = "Work in Progress", Owner = "person1", Due.Date = "2014-08-14",days.left = -24), row.names = c(NA, -1L), .Names = c("Record.ID","Record.Type","Short.Description", "Record.State", "Owner","Due.Date", "days.left"), class = "data.frame")
  print(xtable(test4,display=c("d","d","s","s","s","s","s","d")),include.rownames=F,floating=F,type="html")
  </code></pre>
  
  <p>How can I get xtable to print even though I will have weird characters like this?</p>
  
  <p>FYI, the same operation works without errors when I run it on windows.
  On debian linux, I get the error. Also I checked my locale and it is set correctly.</p>