i_sound.c needs -lm for pow()

--- doomlegacy-1.44/src/Makefile~	2011-01-20 03:20:12.000000000 +0200
+++ doomlegacy-1.44/src/Makefile	2011-01-20 03:21:30.240842662 +0200
@@ -115,7 +115,7 @@
   else
     # default is Linux
     OPTS := -DLINUX
-    LIBS := -lGL -lGLU
+    LIBS := -lGL -lGLU -lm
   endif
 
   OPTS += -DHWRENDER -DSDL $(shell sdl-config --cflags) -I.