Add eddsa from ref10 implementation (with some modifications).

core/crypto/ed25519/ge_sub.q

@@ -0,0 +1,49 @@
+:name:fe:r->X:r->Y:r->Z:r->T:t0:t1:t2:t3:t4:t5:p->X:p->Y:p->Z:p->T:q->YplusX:q->YminusX:q->Z:q->T2d:
+fe r:var/r=fe:
+
+enter f:enter/f:>X1=fe#11:>Y1=fe#12:>Z1=fe#13:>T1=fe#14:>YpX2=fe#15:>YmX2=fe#16:>Z2=fe#17:>T2d2=fe#18:
+return:nofallthrough:<X3=fe#1:<Y3=fe#2:<Z3=fe#3:<T3=fe#4:leave:
+
+h=f+g:<f=fe:<g=fe:>h=fe:asm/fe_add(>h,<f,<g);:
+h=f-g:<f=fe:<g=fe:>h=fe:asm/fe_sub(>h,<f,<g);:
+h=f*g:<f=fe:<g=fe:>h=fe:asm/fe_mul(>h,<f,<g);:
+h=f^2:<f=fe:>h=fe:asm/fe_sq(>h,<f);:
+h=2*g:<g=fe:>h=fe:asm/fe_add(>h,<g,<g);:
+
+:
+
+enter ge_sub
+
+fe X1
+fe Y1
+fe Z1
+fe Z2
+fe T1
+fe ZZ
+fe YpX2
+fe YmX2
+fe T2d2
+fe X3
+fe Y3
+fe Z3
+fe T3
+fe YpX1
+fe YmX1
+fe A
+fe B
+fe C
+fe D
+
+YpX1 = Y1+X1
+YmX1 = Y1-X1
+A = YpX1*YmX2
+B = YmX1*YpX2
+C = T2d2*T1
+ZZ = Z1*Z2
+D = 2*ZZ
+X3 = A-B
+Y3 = A+B
+Z3 = D-C
+T3 = D+C
+
+return