Fix contrib/minizip compilation in the MinGW environment.

contrib/minizip/Makefile.am

@@ -10,11 +10,17 @@ zlib_top_builddir = $(top_builddir)/../..
 AM_CPPFLAGS = -I$(zlib_top_srcdir)
 AM_LDFLAGS = -L$(zlib_top_builddir)
 
+if WIN32
+iowin32_src = iowin32.c
+iowin32_h = iowin32.h
+endif
+
 libminizip_la_SOURCES = \
 	ioapi.c \
 	mztools.c \
 	unzip.c \
-	zip.c
+	zip.c \
+	${iowin32_src}
 
 libminizip_la_LDFLAGS = $(AM_LDFLAGS) -version-info 1:0:0 -lz
 
@@ -24,7 +30,8 @@ minizip_include_HEADERS = \
 	ioapi.h \
 	mztools.h \
 	unzip.h \
-	zip.h
+	zip.h \
+	${iowin32_h}
 
 pkgconfigdir = $(libdir)/pkgconfig
 pkgconfig_DATA = minizip.pc