Don't mark Firefox as a mobile in Windows XP.

Thanks to @connor-prodege for spotting this issue. Fixes #15

all_test.go

@@ -48,6 +48,7 @@ var uastrings = []struct {
  {"AndroidFirefoxTablet", "Mozilla/5.0 (Android; Tablet; rv:26.0) Gecko/26.0 Firefox/26.0"},
  {"FirefoxOS", "Mozilla/5.0 (Mobile; rv:26.0) Gecko/26.0 Firefox/26.0"},
  {"FirefoxOSTablet", "Mozilla/5.0 (Tablet; rv:26.0) Gecko/26.0 Firefox/26.0"},
+ {"FirefoxWinXP", "Mozilla/5.0 (Windows NT 5.2; rv:31.0) Gecko/20100101 Firefox/31.0"},
 
  // Opera
  {"OperaMac", "Opera/9.27 (Macintosh; Intel Mac OS X; U; en)"},
@@ -128,6 +129,7 @@ var expected = []string{
  "Mozilla:5.0 Platform:Tablet OS:Android Browser:Firefox-26.0 Engine:Gecko-26.0 Bot:false Mobile:true",
  "Mozilla:5.0 Platform:Mobile OS:FirefoxOS Browser:Firefox-26.0 Engine:Gecko-26.0 Bot:false Mobile:true",
  "Mozilla:5.0 Platform:Tablet OS:FirefoxOS Browser:Firefox-26.0 Engine:Gecko-26.0 Bot:false Mobile:true",
+ "Mozilla:5.0 Platform:Windows OS:Windows XP x64 Edition Browser:Firefox-31.0 Engine:Gecko-20100101 Bot:false Mobile:false",
 
  // Opera
  "Platform:Macintosh OS:Intel Mac OS X Localization:en Browser:Opera-9.27 Engine:Presto Bot:false Mobile:false",

operating_systems.go

@@ -113,7 +113,7 @@ func gecko(p *UserAgent, comment []string) {
  if p.platform == "Android" {
  p.mobile = true
  p.platform, p.os = normalizeOS(comment[1]), p.platform
- } else if len(comment) < 3 {
+ } else if comment[0] == "Mobile" || comment[0] == "Tablet" {
  p.mobile = true
  p.os = "FirefoxOS"
  } else {