Allow any order of characters in the mode

Author: certik

src/stdlib_experimental_io.f90

@@ -371,6 +371,11 @@ integer function open(filename, mode) result(u)
         mode_(3:3) = mode(3:3)
 end if
 
+if (mode_(1:1) == 'b') then
+    mode_(1:1) = mode_(3:3)
+    mode_(3:3) = 'b'
+end if
+
 end function
 
 end module

src/tests/io/test_open.f90

@@ -95,11 +95,11 @@ subroutine test_parse_mode()
     call assert(m == "a b")
 
     m = parse_mode("br")
-    !call assert(m == "r b")
+    call assert(m == "r b")
     m = parse_mode("bw")
-    !call assert(m == "w b")
+    call assert(m == "w b")
     m = parse_mode("ba")
-    !call assert(m == "a b")
+    call assert(m == "a b")
 
     m = parse_mode("r+")
     call assert(m == "r+t")