Correct Windows/Cygwin build error as reported in issue #603

[DavidKeller]

Prevents wrong quote surrounding that leads to

fatal error C1083: Cannot open include file: 'fficonfig.h': No such file or directory

[lgoldstein]

Better, but it now fails at some other location:

     [exec] cl -MT -nologo -W3 -DHAVE_PROTECTION -DPSAPI_VERSION='1' -DFFI_BUILDING -DUNICODE -D_UNICODE -I"C:\Program Files\Java\jdk1.8.0_102\jre/../include" -I"C:\Program Files\Java\jdk1.8.0_102\jre/../include/win32" -I"D:\Projects\jna\master\build\native-win32-x86-64" -I"../build/native-win32-x86-64/libffi/include" -DJNA_JNI_VERSION='"5.0.0"' -DCHECKSUM='"4f72f2799dfee6008a386bc40afd7428"' -c callback.c -Fo../build/native-win32-x86-64/callback.o -FdD:/Projects/jna/master/build/native-win32-x86-64/callback -FpD:/Projects/jna/master/build/native-win32-x86-64/callback -FaD:/Projects/jna/master/build/native-win32-x86-64/callback
     [exec] callback.c
     [exec] d:\projects\jna\master\native\snprintf.h(5): error C2375: 'snprintf': redefinition; different linkage
     [exec] C:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt\stdio.h(1932): note: see declaration of 'snprintf'
     [exec] x86_64-w64-mingw32-windres -i ../build/native-win32-x86-64/jnidispatch.rc -o ../build/native-win32-x86-64/rsrc.o \
     [exec]           || (echo > ../build/native-win32-x86-64/rsrc.o.c && /d/Projects/jna/master/native/libffi/msvcc.sh
-m64 -W -Wall -Wno-unused -Wno-parentheses    -DHAVE_PROTECTION -DPSAPI_VERSION=1 -DFFI_BUILDING -DUNICODE -D_UNICODE -DUSE_STATIC_RTL -I"C:\Program Files\Java\jdk1.8.0_102\jre/../include" -I"C:\Program Files\Java\jdk1.8.0_102\jre/../include/win32" -I"D:\Projects\jna\master\build\native-win32-x86-64" -I../build/native-win32-x86-64/libffi/include -DJNA_JNI_VERSION='"5.0.0"' -DCHECKSUM='"4f72f2799dfee6008a386bc40afd7428"' -c ../build/native-win32-x86-64/rsrc.o.c -o ../build/native-win32-x86-64/rsrc.o)
     [exec] x86_64-w64-mingw32-gcc -DDEFINE_CALLBACKS -c dll-callback.c -o ../build/native-win32-x86-64/dll-callback.o
     [exec] link /DLL /OUT:../build/native-win32-x86-64/jnidispatch.dll ../build/native-win32-x86-64/dispatch.o ../build/native-win32-x86-64/callback.o ../build/native-win32-x86-64/rsrc.o ../build/native-win32-x86-64/dll-callback.o ../build/native-win32-x86-64/libffi/.libs/libffi.lib psapi.lib
     [exec] Microsoft (R) Incremental Linker Version 14.00.23506.0
     [exec] Copyright (C) Microsoft Corporation.  All rights reserved.
     [exec]
     [exec] LINK : fatal error LNK1181: cannot open input file '../build/native-win32-x86-64/dispatch.o'
     [exec] Makefile:433: recipe for target '../build/native-win32-x86-64/jnidispatch.dll' failed
     [exec] make: *** [../build/native-win32-x86-64/jnidispatch.dll] Error 157

BUILD FAILED
D:\Projects\jna\master\build.xml:820: exec returned: 2

[DavidKeller]

dispatch.o is not compiled because error C2375: 'snprintf': redefinition; different linkage

You may want to apply #669 as well, or only native/snprintf.h modification from c74e734.

[matthiasblaesing]

This is verified - I just merged #669 into a local working branch and was just running unittests on win32-x86 and win32-x64. Unittests work ok. I'll merge #669 and #700 on the weekend.