New year (2023)

Also, small tweak in makefile. (-Wsign-compare is already enabled by
-Wextra.)

makefile

@@ -8,7 +8,6 @@ CWARNSCPP= \
 	-Wfatal-errors \
 	-Wextra \
 	-Wshadow \
-	-Wsign-compare \
 	-Wundef \
 	-Wwrite-strings \
 	-Wredundant-decls \
@@ -60,7 +59,7 @@ CWARNS= $(CWARNSCPP) $(CWARNSC) $(CWARNGCC)
 
 # The following options help detect "undefined behavior"s that seldom
 # create problems; some are only available in newer gcc versions. To
-# use some of them, we also have to define an enrivonment variable
+# use some of them, we also have to define an environment variable
 # ASAN_OPTIONS="detect_invalid_pointer_pairs=2".
 # -fsanitize=undefined
 # -fsanitize=pointer-subtract -fsanitize=address -fsanitize=pointer-compare