Libguestfs - Aug 2016 - [PATCH 1.32] mllib: Add String.map function for OCaml < 4.00.0.

Same patch as just posted, but this is the modified version
required for the stable-1.32 branch.

Rich.

String.map was added in OCaml 4.00.0.  However we use this function
to implement String.lowercase_ascii etc.

Therefore include a definition of the function for older versions of
OCaml.  (Debian Wheezy has OCaml 3.12.1.)

(cherry picked from commit 5802c7750ee47b12a0497b45d8ca52e347328207)
---
 mllib/common_utils.ml  | 8 ++++++++
 mllib/common_utils.mli | 2 ++
 2 files changed, 10 insertions(+)

diff --git a/mllib/common_utils.ml b/mllib/common_utils.ml
index 2ba8f9a..4f56c91 100644
--- a/mllib/common_utils.ml
+++ b/mllib/common_utils.ml
@@ -37,6 +37,14 @@ end
 module String = struct
     include String
 
+    let map f s +      let len = String.length s in
+      let b = String.create len in
+      for i = 0 to len-1 do
+        unsafe_set b i (f (unsafe_get s i))
+      done;
+      b
+
     let lowercase_ascii s = map Char.lowercase_ascii s
     let uppercase_ascii s = map Char.uppercase_ascii s
 
diff --git a/mllib/common_utils.mli b/mllib/common_utils.mli
index ae89fd6..33a46bb 100644
--- a/mllib/common_utils.mli
+++ b/mllib/common_utils.mli
@@ -56,6 +56,8 @@ module String : sig
     val unsafe_get : string -> int -> char
     val unsafe_set : string -> int -> char -> unit
 
+    val map : (char -> char) -> string -> string
+
     val lowercase_ascii : string -> string
     val uppercase_ascii : string -> string
 
-- 
2.7.4