fix several -Wcast-qual warnings

src/json.c:609:40: warning: cast from 'const char *' to 'char *' drops const qualifier [-Wcast-qual]
    escape_json_output (json, (char *) conf.filenames[idx]);
                                       ^
1 warning generated.

src/output.c:215:30: warning: cast from 'const char *' to 'char *' drops const qualifier [-Wcast-qual]
  clean_output (fp, (char *) title);
                             ^
1 warning generated.

src/sort.c:125:30: warning: cast from 'const void *' to 'char **' drops const qualifier [-Wcast-qual]
  return strcmp (*((char **) a), *((char **) b));
                             ^
src/sort.c:125:46: warning: cast from 'const void *' to 'char **' drops const qualifier [-Wcast-qual]
  return strcmp (*((char **) a), *((char **) b));
                                             ^
2 warnings generated.

src/util.c:925:25: warning: cast from 'const char *' to 'unsigned char *' drops const qualifier [-Wcast-qual]
  p = (unsigned char *) src;
                        ^
1 warning generated.

src/websocket.c:260:25: warning: cast from 'const char *' to 'unsigned char *' drops const qualifier [-Wcast-qual]
  p = (unsigned char *) src;
                        ^
src/websocket.c:1513:33: warning: cast from 'const char *' to 'unsigned char *' drops const qualifier [-Wcast-qual]
  SHA1Update (&sha, (uint8_t *) s, len);
                                ^
2 warnings generated.

src/json.c

@@ -218,7 +218,7 @@ fpjson (FILE * fp, const char *fmt, ...)
 
 /* Escape all other characters accordingly. */
 static void
-escape_json_other (GJSON * json, char **s)
+escape_json_other (GJSON * json, const char **s)
 {
   /* Since JSON data is bootstrapped into the HTML document of a report,
    * then we perform the following four translations in case weird stuff
@@ -273,7 +273,7 @@ escape_json_other (GJSON * json, char **s)
  *
  * On success, escaped JSON data is outputted. */
 static void
-escape_json_output (GJSON * json, char *s)
+escape_json_output (GJSON * json, const char *s)
 {
   while (*s) {
     switch (*s) {
@@ -606,7 +606,7 @@ poverall_log_path (GJSON * json, int idx, int isp)
   if (conf.filenames[idx][0] == '-' && conf.filenames[idx][1] == '\0')
     pjson (json, "STDIN");
   else
-    escape_json_output (json, (char *) conf.filenames[idx]);
+    escape_json_output (json, conf.filenames[idx]);
   pjson (json, conf.filenames_idx - 1 != idx ? "\",\n" : "\"");
 }
 

src/output.c

@@ -169,7 +169,7 @@ panel_lookup (GModule module)
 
 /* Sanitize output with html entities for special chars */
 static void
-clean_output (FILE * fp, char *s)
+clean_output (FILE * fp, const char *s)
 {
   if (!s) {
     LOG_DEBUG (("NULL data on clean_output.\n"));
@@ -212,7 +212,7 @@ print_html_title (FILE * fp)
     conf.html_report_title ? conf.html_report_title : HTML_REPORT_TITLE;
 
   fprintf (fp, "<title>");
-  clean_output (fp, (char *) title);
+  clean_output (fp, title);
   fprintf (fp, "</title>");
 }
 

src/sort.c

@@ -122,7 +122,7 @@ GSort module_sort[TOTAL_MODULES] = {
 int
 strcmp_asc (const void *a, const void *b)
 {
-  return strcmp (*((char **) a), *((char **) b));
+  return strcmp (*((char *const *) a), *((char * const*) b));
 }
 
 /* Sort 'data' metric ascending */

src/util.c

@@ -922,7 +922,7 @@ escape_str (const char *src)
   if (src == NULL || *src == '\0')
     return NULL;
 
-  p = (unsigned char *) src;
+  p = (const unsigned char *) src;
   q = dest = xmalloc (strlen (src) * 4 + 1);
 
   while (*p) {

src/websocket.c

@@ -257,7 +257,7 @@ escape_http_request (const char *src)
   if (src == NULL || *src == '\0')
     return NULL;
 
-  p = (unsigned char *) src;
+  p = (const unsigned char *) src;
   q = dest = xmalloc (strlen (src) * 4 + 1);
 
   while (*p) {
@@ -1505,7 +1505,7 @@ http_error (WSClient * client, const char *buffer)
 
 /* Compute the SHA1 for the handshake. */
 static void
-ws_sha1_digest (const char *s, int len, unsigned char *digest)
+ws_sha1_digest (char *s, int len, unsigned char *digest)
 {
   SHA1_CTX sha;