Fix compilation failures: get rid of C++ specifics in C-code.

client/mysql_upgrade.c

@@ -234,7 +234,7 @@ get_one_option(int optid, const struct my_option *opt,
 
   case 'p':
     if (argument == disabled_my_option)
-      argument= (char*) "";			// Don't require password
+      argument= (char*) "";			/* Don't require password */
     tty_password= 1;
     add_option= FALSE;
     if (argument)

client/mysqlcheck.c

@@ -287,7 +287,7 @@ get_one_option(int optid, const struct my_option *opt __attribute__((unused)),
     break;
   case 'p':
     if (argument == disabled_my_option)
-      argument= (char*) "";			// Don't require password
+      argument= (char*) "";			/* Don't require password */
     if (argument)
     {
       char *start = argument;

client/mysqldump.c

@@ -703,7 +703,7 @@ get_one_option(int optid, const struct my_option *opt __attribute__((unused)),
 #endif
   case 'p':
     if (argument == disabled_my_option)
-      argument= (char*) "";                     // Don't require password
+      argument= (char*) "";                     /* Don't require password */
     if (argument)
     {
       char *start=argument;

client/mysqlimport.c

@@ -222,7 +222,7 @@ get_one_option(int optid, const struct my_option *opt __attribute__((unused)),
 #endif
   case 'p':
     if (argument == disabled_my_option)
-      argument= (char*) "";			// Don't require password
+      argument= (char*) "";			/* Don't require password */
     if (argument)
     {
       char *start=argument;

client/mysqlshow.c

@@ -282,7 +282,7 @@ get_one_option(int optid, const struct my_option *opt __attribute__((unused)),
     break;
   case 'p':
     if (argument == disabled_my_option)
-      argument= (char*) "";			// Don't require password
+      argument= (char*) "";			/* Don't require password */
     if (argument)
     {
       char *start=argument;

client/mysqlslap.c

@@ -713,7 +713,7 @@ get_one_option(int optid, const struct my_option *opt __attribute__((unused)),
     break;
   case 'p':
     if (argument == disabled_my_option)
-      argument= (char*) "";			// Don't require password
+      argument= (char*) "";			/* Don't require password */
     if (argument)
     {
       char *start= argument;