math: add drem and dremf weak aliases to i386 remainder asm

weak_alias was only in the c code, so drem was missing on platforms
where remainder is implemented in asm.

src/math/i386/remainder.s

@@ -1,6 +1,9 @@
 .global remainder
 .type remainder,@function
 remainder:
+.weak drem
+.type drem,@function
+drem:
 	fldl 12(%esp)
 	fldl 4(%esp)
 1:	fprem1

src/math/i386/remainderf.s

@@ -1,6 +1,9 @@
 .global remainderf
 .type remainderf,@function
 remainderf:
+.weak dremf
+.type dremf,@function
+dremf:
 	flds 8(%esp)
 	flds 4(%esp)
 1:	fprem1