Use precomputed table

From jpeglib-turbo r1221:
Integrate a slightly modified version of Mozilla's patch for
precomputing the bit-counting LUT.  This is useful if the table needs
to be shared among multiple processes, although the primary reason for
doing that is reduced footprint on mobile devices, which are probably
already covered by the clz intrinsic code.

jcdctmgr.c

@@ -590,9 +590,7 @@ forward_DCT_float (j_compress_ptr cinfo, jpeg_component_info * compptr,
 #endif /* DCT_FLOAT_SUPPORTED */
 
 #include "jchuff.h"
-
-static unsigned char jpeg_nbits_table[65536];
-static int jpeg_nbits_table_init = 0;
+#include "jpeg_nbits_table.h"
 
 static const float jpeg_lambda_weights_flat[64] = {
   1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f,
@@ -660,15 +658,6 @@ quantize_trellis(j_compress_ptr cinfo, c_derived_tbl *actbl, JBLOCKROW coef_bloc
     requires_eob[0] = 0;
   }
 
-  if(!jpeg_nbits_table_init) {
-    for(i = 0; i < 65536; i++) {
-      int nbits = 0, temp = i;
-      while (temp) {temp >>= 1;  nbits++;}
-      jpeg_nbits_table[i] = nbits;
-    }
-    jpeg_nbits_table_init = 1;
-  }
-
   norm = 0.0;
   for (i = 1; i < DCTSIZE2; i++) {
     norm += qtbl->quantval[i] * qtbl->quantval[i];

jchuff.c

@@ -22,8 +22,7 @@
 #include "jchuff.h"		/* Declarations shared with jcphuff.c */
 #include <limits.h>
 
-static unsigned char jpeg_nbits_table[65536];
-static int jpeg_nbits_table_init = 0;
+#include "jpeg_nbits_table.h"
 
 #ifndef min
  #define min(a,b) ((a)<(b)?(a):(b))
@@ -271,15 +270,6 @@ jpeg_make_c_derived_tbl (j_compress_ptr cinfo, boolean isDC, int tblno,
     dtbl->ehufco[i] = huffcode[p];
     dtbl->ehufsi[i] = huffsize[p];
   }
-
-  if(!jpeg_nbits_table_init) {
-    for(i = 0; i < 65536; i++) {
-      int nbits = 0, temp = i;
-      while (temp) {temp >>= 1;  nbits++;}
-      jpeg_nbits_table[i] = nbits;
-    }
-    jpeg_nbits_table_init = 1;
-  }
 }