There is no reason to use PL/pgSQL if you do not use one or more features of a procedural language

SELECT 
  pg_namespace.nspname AS routine_schema, 
  pg_proc.proname AS routine_name, 
  pg_get_function_identity_arguments(pg_proc.oid) AS parameters,
  CASE WHEN pg_proc.prokind='f' THEN 'FUNCTION'
  WHEN pg_proc.prokind='p' THEN 'PROCEDURE'
  WHEN pg_proc.prokind='w' THEN 'WINDOW FUNCTION' END AS routine_type,
  regexp_replace(pg_get_functiondef(pg_proc.oid),'[\r\n]','<br>','g')  AS routine_src
FROM 
  pg_catalog.pg_proc, 
  pg_catalog.pg_namespace,
  pg_catalog.pg_language,
  pg_catalog.pg_type
WHERE 
  pg_proc.pronamespace = pg_namespace.oid 
  AND pg_proc.prolang = pg_language.oid 
  AND pg_type.oid=pg_proc.prorettype 
  AND pg_language.lanname='plpgsql' 
  AND pg_type.typname<>'trigger' 
  AND pg_proc.prokind<>'a'
  AND pg_proc.proname NOT IN ('f_assume_you_must_use_files', 'f_check_format_comma_separated_list', 'f_check_password', 'f_default_value_with_no_match') 
  AND (pg_get_functiondef(pg_proc.oid)!~*'DECLARE[[:space:]]' OR pg_get_functiondef(pg_proc.oid)~*'DECLARE[[:space:]]+BEGIN') 
  AND pg_get_functiondef(pg_proc.oid)!~*'[[:space:]](SELECT[[:space:]]+INTO|IF|ELSIF|WHILE|FOR|END[[:space:]]+LOOP|FOREACH|CASE|RAISE|EXCEPTION|CURSOR|OPEN|FETCH|MOVE|CLOSE|GET[[:space:]]+STACKED[[:space:]]+DIAGNOSTICS)[[:space:]]'
 AND pg_namespace.nspname NOT IN (SELECT schema_name
FROM INFORMATION_SCHEMA.schemata
WHERE schema_name<>'public' AND
schema_owner='postgres' AND schema_name IS NOT NULL)
ORDER BY routine_schema, routine_name, parameters;