[uchardet] src: give a little weight to "probable sequences".

[Jehan Pagès <jehanp src gnome org>]

commit e0eec3bae8409d528458c8b69ffd18ff6a52bc94
Author: Jehan <jehan girinstud io>
Date:   Wed May 25 17:24:37 2016 +0200

    src: give a little weight to "probable sequences".
    
    Up to now, we were only considering positive sequences, which are
    sequences of 2 characters which happen the most. Yet our data gather
    4 categories of sequences (the last one being called "negative", since
    they never happened in our data).
    I will call the category below positive: probable sequences. They may
    happen, yet not often. The last category could be called "neutral".
    This seems to fix the detection of a user's subtitle example without
    breaking any of our current unit tests.
    Probably I should still review this whole logics more in details later.

 src/nsSBCharSetProber.cpp |    2 +-
 src/nsSBCharSetProber.h   |    3 +++
 2 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/src/nsSBCharSetProber.cpp b/src/nsSBCharSetProber.cpp
index cb00fbc..1f7f473 100644
--- a/src/nsSBCharSetProber.cpp
+++ b/src/nsSBCharSetProber.cpp
@@ -124,7 +124,7 @@ float nsSingleByteCharSetProber::GetConfidence(void)
      * character). This could make the difference between very closely related
      * charsets used for the same language.
      */
-    r = r*mSeqCounters[POSITIVE_CAT] / mTotalChar;
+    r = r * (mSeqCounters[POSITIVE_CAT] + (float) mSeqCounters[PROBABLE_CAT] / 4) / mTotalChar;
     /* The more control characters (proportionnaly to the size of the text), the
      * less confident we become in the current charset.
      */
diff --git a/src/nsSBCharSetProber.h b/src/nsSBCharSetProber.h
index fb40d3f..211846e 100644
--- a/src/nsSBCharSetProber.h
+++ b/src/nsSBCharSetProber.h
@@ -57,8 +57,11 @@
 #define POSITIVE_SHORTCUT_THRESHOLD  (float)0.95
 #define NEGATIVE_SHORTCUT_THRESHOLD  (float)0.05
 #define SYMBOL_CAT_ORDER  250
+
 #define NUMBER_OF_SEQ_CAT 4
 #define POSITIVE_CAT   (NUMBER_OF_SEQ_CAT-1)
+#define PROBABLE_CAT   (NUMBER_OF_SEQ_CAT-2)
+#define NEUTRAL_CAT    (NUMBER_OF_SEQ_CAT-3)
 #define NEGATIVE_CAT   0
 
 typedef struct