Remove code from libgcc and libc that is provided by the ROM.

This saves about 2.5k of iram.

lib/libgcc.remove

@@ -0,0 +1,24 @@
+# Object files to be removed from libgcc
+# These are provided by the ROM.
+_addsubdf3.o
+_addsubsf3.o
+_divdf3.o
+_divdi3.o
+_divsi3.o
+_extendsfdf2.o
+_fixdfsi.o
+_fixunssfsi.o
+_floatsidf.o
+_floatsisf.o
+_floatunsidf.o
+_floatunsisf.o
+_muldf3.o
+_muldi3.o
+_mulsf3.o
+_subdf3.o
+_subsf3.o
+_truncdfsf2.o
+_udivdi3.o
+_umoddi3.o
+_umodsi3.o
+_umulsidi3.o