Looking at the ed25519 code, these defines are unused. They appear to be unused upstream as well (in djt's supercop ed25519/ref implementation), so maybe this should be suggested there instead of deviating. Up to you.
Index: usr.bin/signify/fe25519.c =================================================================== RCS file: /cvs/src/usr.bin/signify/fe25519.c,v retrieving revision 1.1 diff -u -p -u -r1.1 fe25519.c --- usr.bin/signify/fe25519.c 22 Jul 2014 00:41:19 -0000 1.1 +++ usr.bin/signify/fe25519.c 9 Nov 2018 05:58:45 -0000 @@ -6,9 +6,6 @@ * Copied from supercop-20130419/crypto_sign/ed25519/ref/fe25519.c */ -#define WINDOWSIZE 1 /* Should be 1,2, or 4 */ -#define WINDOWMASK ((1<<WINDOWSIZE)-1) - #include "fe25519.h" static crypto_uint32 equal(crypto_uint32 a,crypto_uint32 b) /* 16-bit inputs */ Index: usr.bin/ssh/fe25519.c =================================================================== RCS file: /cvs/src/usr.bin/ssh/fe25519.c,v retrieving revision 1.3 diff -u -p -u -r1.3 fe25519.c --- usr.bin/ssh/fe25519.c 9 Dec 2013 11:03:45 -0000 1.3 +++ usr.bin/ssh/fe25519.c 9 Nov 2018 05:58:45 -0000 @@ -6,9 +6,6 @@ * Copied from supercop-20130419/crypto_sign/ed25519/ref/fe25519.c */ -#define WINDOWSIZE 1 /* Should be 1,2, or 4 */ -#define WINDOWMASK ((1<<WINDOWSIZE)-1) - #include "fe25519.h" static crypto_uint32 equal(crypto_uint32 a,crypto_uint32 b) /* 16-bit inputs */
