fix Makefile and README.md for 2000/schneiderwent

NOTE: This program does not compile.

2000/schneiderwent/Makefile

@@ -75,8 +75,8 @@ CWARN= -Wall -Wextra -pedantic ${CSILENCE}
 # Compiler standard
 #
 #CSTD=
-CSTD= -ansi
-#CSTD= -std=gnu99
+#CSTD= -ansi
+CSTD= -std=gnu99
 
 # Compiler bit architecture
 #
@@ -101,7 +101,7 @@ CINCLUDE=
 #CINCLUDE= -include stdlib.h
 #CINCLUDE= -include stdio.h
 #CINCLUDE= -include stdlib.h -include stdio.h
-#CINCLUDE= -I ${X11_INCDIR}
+#CINCLUDE= -I ${X11_INCDIR} -I ${X11_INCDIR}/X11
 #CINCLUDE= `${SDL2_CONFIG} --cflags`
 
 # Optimization
@@ -138,8 +138,7 @@ CC= cc
 #
 ifeq ($(CC),clang)
 #
-CSILENCE+= -Wno-missing-variable-declarations -Wno-poison-system-directories \
-	-Wno-shorten-64-to-32 -Wno-sign-conversion
+CSILENCE+= -Wno-missing-variable-declarations -Wno-poison-system-directories
 #
 CWARN+= -Weverything
 #
@@ -324,4 +323,3 @@ pluto: charon
 	@echo "dwarf is a type of planet"
 	@echo "therefore, $@ is a planet"
 	@echo "having lots of planets is good feature because supernovae can help ${MAKE} a lot of them"
-