Fix compiler warnings (-Wstringop-truncation)

gcc warnings:

    src/api/tesseractmain.cpp:252:14: warning:
        ‘char* strncpy(char*, const char*, size_t)’ specified bound 255
        equals destination size [-Wstringop-truncation]
    src/ccutil/unicharset.h:66:12: warning:
        ‘char* strncpy(char*, const char*, size_t)’ output may be truncated copying 30 bytes from a string of length 30 [-Wstringop-truncation]
    src/ccutil/unicharset.cpp:806:12: warning:
        ‘char* strncpy(char*, const char*, size_t)’ specified bound 64 equals destination size [-Wstringop-truncation]

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

src/api/tesseractmain.cpp

@@ -249,7 +249,7 @@ static void SetVariablesFromCLArgs(tesseract::TessBaseAPI* api, int argc,
         exit(EXIT_FAILURE);
       }
       *p = 0;
-      strncpy(opt2, strchr(argv[i + 1], '=') + 1, 255);
+      strncpy(opt2, strchr(argv[i + 1], '=') + 1, sizeof(opt2) - 1);
       opt2[254] = 0;
       ++i;
 

src/ccutil/unicharset.cpp

@@ -803,7 +803,7 @@ bool UNICHARSET::load_via_fgets(
     unsigned int properties;
     char script[64];
 
-    strncpy(script, null_script, sizeof(script));
+    strncpy(script, null_script, sizeof(script) - 1);
     int min_bottom = 0;
     int max_bottom = UINT8_MAX;
     int min_top = 0;

src/ccutil/unicharset.h

@@ -63,7 +63,7 @@ class CHAR_FRAGMENT {
     set_natural(natural);
   }
   inline void set_unichar(const char *uch) {
-    strncpy(this->unichar, uch, UNICHAR_LEN);
+    strncpy(this->unichar, uch, sizeof(this->unichar));
     this->unichar[UNICHAR_LEN] = '\0';
   }
   inline void set_pos(int p) { this->pos = p; }