Fix compiler warnings [-Wunused-const-variable]

clang warnings:

src/classify/trainingsampleset.cpp:39:11: warning:
 unused variable 'kMinOutlierSamples' [-Wunused-const-variable]
src/lstm/lstmrecognizer.cpp:45:11: warning:
 unused variable 'kMaxChoices' [-Wunused-const-variable]
src/training/dawg2wordlist.cpp:28:11: warning:
 unused variable 'kDictDebugLevel' [-Wunused-const-variable]
src/training/stringrenderer.cpp:50:21: warning:
 unused variable 'kWordJoiner' [-Wunused-const-variable]

Signed-off-by: Stefan Weil <sw@weilnetz.de>

src/classify/trainingsampleset.cpp

@@ -35,8 +35,6 @@ const int kSquareLimit = 25;
 // Prime numbers for subsampling distances.
 const int kPrime1 = 17;
 const int kPrime2 = 13;
-// Min samples from which to start discarding outliers.
-const int kMinOutlierSamples = 5;
 
 TrainingSampleSet::FontClassInfo::FontClassInfo()
   : num_raw_samples(0), canonical_sample(-1), canonical_dist(0.0f) {

src/lstm/lstmrecognizer.cpp

@@ -41,8 +41,6 @@
 
 namespace tesseract {
 
-// Max number of blob choices to return in any given position.
-const int kMaxChoices = 4;
 // Default ratio between dict and non-dict words.
 const double kDictRatio = 2.25;
 // Default certainty offset to give the dictionary a chance.

src/training/dawg2wordlist.cpp

@@ -25,8 +25,6 @@
 #include "trie.h"
 #include "unicharset.h"
 
-const int kDictDebugLevel = 1;
-
 tesseract::Dawg *LoadSquishedDawg(const UNICHARSET &unicharset,
                                   const char *filename) {
   const int kDictDebugLevel = 1;

src/training/stringrenderer.cpp

@@ -47,7 +47,6 @@ static const int kDefaultOutputResolution = 300;
 // recommendation in http://unicode.org/reports/tr14/ to avoid line-breaks at
 // hyphens and other non-alpha characters.
 static const char* kWordJoinerUTF8 = "\u2060";
-static const char32 kWordJoiner = 0x2060;
 
 static bool IsCombiner(int ch) {
   const int char_type = u_charType(ch);