Fix Windows GZip linking

QGCExternalLibs.pri

@@ -113,8 +113,10 @@ SOURCES += \
 WindowsBuild {
     INCLUDEPATH +=  $$SOURCE_DIR/libs/zlib/windows/include
     LIBS += -L$$SOURCE_DIR/libs/zlib/windows/lib
+    LIBS += -lzlibstat
+} else {
+    LIBS += -lz
 }
-LIBS += -lz
 
 #
 # [REQUIRED] SDL dependency. Provides joystick/gamepad support.

libs/zlib/windows/lib/README

@@ -0,0 +1 @@
+Prebuilt version comes from here: http://www.winimage.com/zLibDll/

libs/zlib/windows/lib/zlib.def

@@ -1,75 +0,0 @@
-; h:\mingw\3.3.1\bin\dlltool.exe --export-all-symbols --output-def=zlib.def adler32.pic.o compress.pic.o crc32.pic.o gzio.pic.o uncompr.pic.o deflate.pic.o trees.pic.o zutil.pic.o inflate.pic.o infback.pic.o inftrees.pic.o inffast.pic.o zlib-dllversion.o zlib-dll-res.o
-EXPORTS
-	DllGetVersion @ 1 ; 
-	_dist_code @ 2 DATA ; 
-	_length_code @ 3 DATA ; 
-	_tr_align @ 4 ; 
-	_tr_flush_block @ 5 ; 
-	_tr_init @ 6 ; 
-	_tr_stored_block @ 7 ; 
-	_tr_tally @ 8 ; 
-	adler32 @ 9 ; 
-	adler32_combine @ 10 ; 
-	compress @ 11 ; 
-	compress2 @ 12 ; 
-	compressBound @ 13 ; 
-	crc32 @ 14 ; 
-	crc32_combine @ 15 ; 
-	deflate @ 16 ; 
-	deflateBound @ 17 ; 
-	deflateCopy @ 18 ; 
-	deflateEnd @ 19 ; 
-	deflateInit2_ @ 20 ; 
-	deflateInit_ @ 21 ; 
-	deflateParams @ 22 ; 
-	deflatePrime @ 23 ; 
-	deflateReset @ 24 ; 
-	deflateSetDictionary @ 25 ; 
-	deflateSetHeader @ 26 ; 
-	deflateTune @ 27 ; 
-	deflate_copyright @ 28 DATA ; 
-	get_crc_table @ 29 ; 
-	gzclearerr @ 30 ; 
-	gzclose @ 31 ; 
-	gzdirect @ 32 ; 
-	gzdopen @ 33 ; 
-	gzeof @ 34 ; 
-	gzerror @ 35 ; 
-	gzflush @ 36 ; 
-	gzgetc @ 37 ; 
-	gzgets @ 38 ; 
-	gzopen @ 39 ; 
-	gzprintf @ 40 ; 
-	gzputc @ 41 ; 
-	gzputs @ 42 ; 
-	gzread @ 43 ; 
-	gzrewind @ 44 ; 
-	gzseek @ 45 ; 
-	gzsetparams @ 46 ; 
-	gztell @ 47 ; 
-	gzungetc @ 48 ; 
-	gzwrite @ 49 ; 
-	inflate @ 50 ; 
-	inflateBack @ 51 ; 
-	inflateBackEnd @ 52 ; 
-	inflateBackInit_ @ 53 ; 
-	inflateCopy @ 54 ; 
-	inflateEnd @ 55 ; 
-	inflateGetHeader @ 56 ; 
-	inflateInit2_ @ 57 ; 
-	inflateInit_ @ 58 ; 
-	inflatePrime @ 59 ; 
-	inflateReset @ 60 ; 
-	inflateSetDictionary @ 61 ; 
-	inflateSync @ 62 ; 
-	inflateSyncPoint @ 63 ; 
-	inflate_copyright @ 64 DATA ; 
-	inflate_fast @ 65 ; 
-	inflate_table @ 66 ; 
-	uncompress @ 67 ; 
-	zError @ 68 ; 
-	z_errmsg @ 69 DATA ; 
-	zcalloc @ 70 ; 
-	zcfree @ 71 ; 
-	zlibCompileFlags @ 72 ; 
-	zlibVersion @ 73 ;