add support for 32-bit ARM on Windows (#477)

* add support for 32-bit ARM on Windows

* fix mismatched brace in appveyor.yml

* remove arm platform from appveyor.yml for now

* fix arm build

* fix typo

* fix assembler names

* try Visual Studio 2017

* add windows arm32 to .appveyor.yml

* update README.md

README.md

@@ -56,6 +56,7 @@ tested:
 | ARC             | Linux            | GCC                     |
 | ARM             | Linux            | GCC                     |
 | ARM             | iOS              | GCC                     |
+| ARM             | Windows          | MSVC                    |
 | AVR32           | Linux            | GCC                     |
 | Blackfin        | uClinux          | GCC                     |
 | HPPA            | HPUX             | GCC                     |
@@ -196,7 +197,8 @@ See the git log for details at http://github.com/libffi/libffi.
         Default to Microsoft's 64 bit long double ABI with Visual C++.
           GNU compiler uses 80 bits (128 in memory) FFI_GNUW64 ABI.
 	Many new tests cases and bug fixes.
-    
+        Add Windows 32-bit arm support.
+        
     3.2.1 Nov-12-14
         Build fix for non-iOS AArch64 targets.