Clang: ISO C++17 does not allow register storage class specifier
https://bugs.gentoo.org/897838
--- a/libs-external/USI++/src/misc.cc
+++ b/libs-external/USI++/src/misc.cc
@@ -18,9 +18,9 @@
 in_cksum (unsigned short *ptr, int nbytes, bool may_pad)
 {
 
-  register long sum;		/* assumes long == 32 bits */
+  long sum;		/* assumes long == 32 bits */
   u_short oddbyte;
-  register u_short answer;	/* assumes u_short == 16 bits */
+  u_short answer;	/* assumes u_short == 16 bits */
 
 
   /* For psuedo-headers: odd len's require