Update 1996/schweikh3/Makefile for SunOS

Rather than make anyone manually update the Makefile (the command in the
README.md file suggested that one would use Makefile variables) or type
a more complicated command the Makefile now tries to compile the entry
as suggested if compilation fails. Thus one can type 'make all' and if
compilation fails it will try the SunOS way.

1996/schweikh3/Makefile

@@ -129,7 +129,8 @@ all: data ${TARGET}
 	sandwich supernova deep_magic magic charon pluto
 
 ${PROG}: ${PROG}.c
-	${CC} ${CFLAGS} $< -o $@ ${LDFLAGS}
+	${CC} ${CFLAGS} $< -o $@ ${LDFLAGS} || \
+	    ${CC} ${CFLAGS} -I. '-Ddifftime(a,b)=(double)(b-a)' $< -o $@ ${LDFLAGS}
 
 # alternative executable
 #

1996/schweikh3/README.md

@@ -33,14 +33,6 @@ But still it is a useful utility.  To use try:
 
 and thanks for the virtual memories!  :-)
 
-NOTE: On some systems such as SunOS, one may need to compile with:
-
-```make
-	${CC} ${CFLAGS} \
-	  -I. -D_POSIX_SOURCE '-Ddifftime(a,b)=(double)(b-a)' \
-	  schweikh3.c -o schweikh3
-```
-
 
 ## Author's remarks:
 

thanks-for-help.md

@@ -2192,6 +2192,13 @@ suggested that one try the longer version too but it will run in an infinite
 loop so having it in a script is less desired).
 
 
+## <a name="1996_schweikh3"></a>[1996/schweikh3](/1996/schweikh3/schweikh3.c) ([README.md](/1996/schweikh3/README.md]))
+
+[Cody](#cody) updated the Makefile so that if it fails to compile it will try he
+method suggested for SunOS rather than having to update the Makefile manually or
+running a more complicated command: now one can just run `make`.
+
+
 ## <a name="1996_westley"></a>[1996/westley](/1996/westley/westley.c) ([README.md](/1996/westley/README.md]))
 
 [Cody](#cody) fixed a segfault in this entry as well as it displaying environmental