Remove warnings and add OS/2 support

README

@@ -75,6 +75,7 @@ tested:
 | X86          | Linux            |
 | X86          | Mac OSX          |
 | X86          | OpenBSD          |
+| X86          | OS/2             |
 | X86          | Solaris          |
 | X86          | Windows/Cygwin   |
 | X86          | Windows/MingW    |
@@ -113,13 +114,9 @@ It's also possible to build libffi on Windows platforms with
 Microsoft's Visual C++ compiler.  In this case, use the msvcc.sh
 wrapper script during configuration like so:
 
-path/to/configure CC=path/to/msvcc.sh LD=link CPP=\"cl -nologo -EP\"
-
-For 64-bit Windows builds, use CC="path/to/msvcc.sh -m64".
-You may also need to specify --build appropriately. When building with MSVC
-under a MingW environment, you may need to remove the line in configure
-that sets 'fix_srcfile_path' to a 'cygpath' command. ('cygpath' is not
-present in MingW, and is not required when using MingW-style paths.)
+path/to/configure --enable-shared --enable-static \
+	CC=path/to/msvcc.sh LD=link \
+	CPP=\"cl -nologo -EP\"
 
 Configure has many other options. Use "configure --help" to see them all.