Correct misspellings of the word "synctex"

Both in the documentation and in function names, "synctex" was sometimes
spelled "syntex" or "syntec".

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>

main.c

@@ -111,7 +111,7 @@ main(int argc, char* argv[])
   }
 
   /* Enable/Disable synctex support */
-  zathura_set_syntex(zathura, synctex);
+  zathura_set_synctex(zathura, synctex);
 
   /* Print version */
   if (print_version == true) {

zathura.1.rst

@@ -48,10 +48,10 @@ OPTIONS
   Set log debug level (debug, info, warning, error)
 
 -s, --synctex
-  Enable syntex support
+  Enable synctex support
 
--x [cmd], --syntec-editor-command [cmd]
-  Set the syntex editor command
+-x [cmd], --synctex-editor-command [cmd]
+  Set the synctex editor command
 
 MOUSE AND KEY BINDINGS
 ======================

zathura.c

@@ -397,7 +397,7 @@ zathura_set_synctex_editor_command(zathura_t* zathura, const char* command)
 }
 
 void
-zathura_set_syntex(zathura_t* zathura, bool value)
+zathura_set_synctex(zathura_t* zathura, bool value)
 {
   g_return_if_fail(zathura != NULL);
   g_return_if_fail(zathura->ui.session != NULL);

zathura.h

@@ -210,12 +210,12 @@ void zathura_set_plugin_dir(zathura_t* zathura, const char* dir);
 void zathura_set_synctex_editor_command(zathura_t* zathura, const char* command);
 
 /**
- * En/Disable zathuras syntex support
+ * En/Disable zathuras synctex support
  *
  * @param zathura The zathura session
  * @param value The value
  */
-void zathura_set_syntex(zathura_t* zathura, bool value);
+void zathura_set_synctex(zathura_t* zathura, bool value);
 
 /**
  * Sets the program parameters