changes to mapfile, read builtins for unbuffered reads

tests/read.right

@@ -30,6 +30,7 @@ argv[1] = <foo>
 argv[1] = <foo>
 argv[1] = < foo>
 a = abcdefg
+xyz
 a = xyz
 a = -xyz 123-
 a = abc
@@ -46,6 +47,7 @@ abcde
 abcde
 ./read3.sub: line 17: read: -1: invalid number
 abc
+defg
 ab
 abc
 #
@@ -76,3 +78,7 @@ unset or null 3
 timeout 4: ok
 abcde
 abcde
+one
+two three four
+one
+two three four