do not require leading . for rl color prefix etension; fix for isearch in single-byte locales; next set of doc updates (SIGNALS); add warning for invalid job id; allow function names to be non-identifiers in posix mode

tests/func.right

@@ -175,7 +175,7 @@ function a=2 ()
 { 
     printf "FUNCNAME: %s\n" $FUNCNAME
 }
-function 11111 () 
+11111 () 
 { 
     printf "FUNCNAME: %s\n" $FUNCNAME
 }
@@ -242,14 +242,13 @@ break ()
 execution
 inside function break
 ./func5.sub: line 86: `break': is a special builtin
-./func5.sub: line 92: `!!': not a valid identifier
 !! is a function
 !! () 
 { 
     fc -s "$@"
 }
 !! is a function
-function !! () 
+!! () 
 { 
     fc -s "$@"
 }