Made winmm a separate shared library.

diff --git a/Make.rules.in b/Make.rules.in
index e2ecbdfc..7618962 100644
--- a/Make.rules.in
+++ b/Make.rules.in
@@ -126,6 +126,7 @@
 	windebug \
 	wineoss.drv \
 	wing \
+	winmm \
 	winspool \
 	wnaspi32 \
 	wsock32