Update ICU to 58.1

source/config/mh-mingw

Index: source/config/mh-mingw
diff --git a/source/config/mh-mingw b/source/config/mh-mingw
index 5e6acad210a440a8394702dab75fb6690e447fa7..b8d2ee0589dc60bef68689879162dc892ebf7a28 100644
--- a/source/config/mh-mingw
+++ b/source/config/mh-mingw
@@ -1,4 +1,6 @@
 ## -*-makefile-*-
+## Copyright (C) 2016 and later: Unicode, Inc. and others.
+## License & terms of use: http://www.unicode.org/copyright.html
 ## Cygwin/MinGW specific setup
 ## Copyright (c) 2001-2014, International Business Machines Corporation and
 ## others. All Rights Reserved.
@@ -66,13 +68,13 @@ SO_TARGET_VERSION_SUFFIX =
 endif
 
 # Static library prefix and file extension
-LIBSICU = lib$(LIBPREFIX)$(STATIC_PREFIX)$(ICUPREFIX)
+LIBSICU = $(LIBPREFIX)$(STATIC_PREFIX)$(ICUPREFIX)
 A = a
 
 ## An import library is needed for z/OS and MSVC
 IMPORT_LIB_EXT = .dll.a
 
-LIBPREFIX=
+LIBPREFIX=lib
 
 # Change the stubnames so that poorly working FAT disks and installation programs can work.
 # This is also for backwards compatibility.