Bug #59275: SHOW PRIVILEGES doesn't have an entry for the PROXY privilege

Added the privilege to the SHOW command.

mysql-test/r/grant.result

@@ -594,6 +594,7 @@ Index	Tables	To create or drop indexes
 Insert	Tables	To insert data into tables
 Lock tables	Databases	To use LOCK TABLES (together with SELECT privilege)
 Process	Server Admin	To view the plain text of currently executing queries
+Proxy	Server Admin	To make proxy user possible
 References	Databases,Tables	To have references on tables
 Reload	Server Admin	To reload or refresh tables, logs and privileges
 Replication client	Server Admin	To ask where the slave or master servers are

sql/sql_show.cc

@@ -336,6 +336,7 @@ static struct show_privileges_st sys_privileges[]=
   {"Insert", "Tables",  "To insert data into tables"},
   {"Lock tables","Databases","To use LOCK TABLES (together with SELECT privilege)"},
   {"Process", "Server Admin", "To view the plain text of currently executing queries"},
+  {"Proxy", "Server Admin", "To make proxy user possible"},
   {"References", "Databases,Tables", "To have references on tables"},
   {"Reload", "Server Admin", "To reload or refresh tables, logs and privileges"},
   {"Replication client","Server Admin","To ask where the slave or master servers are"},