Fix failing sys_vars.plugin_dir_basic - treat both '/' and '\' as path...

Fix failing sys_vars.plugin_dir_basic - treat both '/' and '\' as path separators in get_relative_path() on Windows

include/my_global.h

@@ -818,12 +818,14 @@ typedef SOCKET_SIZE_TYPE size_socket;
 
 #ifdef _WIN32
 #define FN_LIBCHAR	'\\'
+#define FN_LIBCHAR2	'/'
 #define FN_ROOTDIR	"\\"
 #define FN_DEVCHAR	':'
 #define FN_NETWORK_DRIVES	/* Uses \\ to indicate network drives */
 #define FN_NO_CASE_SENCE	/* Files are not case-sensitive */
 #else
 #define FN_LIBCHAR	'/'
+#define FN_LIBCHAR2	'/'
 #define FN_ROOTDIR	"/"
 #endif
 

sql/mysqld.cc

@@ -7681,7 +7681,7 @@ static char *get_relative_path(const char *path)
       strcmp(DEFAULT_MYSQL_HOME,FN_ROOTDIR))
   {
     path+=(uint) strlen(DEFAULT_MYSQL_HOME);
-    while (*path == FN_LIBCHAR)
+    while (*path == FN_LIBCHAR || *path == FN_LIBCHAR2)
       path++;
   }
   return (char*) path;