Improve how 1986/wall alt code is built

Add explicit rule to compile alt code and update CFLAGS to include (if
CC is gcc) -traditional-cpp. Clang does not support it. If CC is cc it
might support it depending on the system (macOS gcc is actually clang so
it won't but linux it will). This allows just running instead of:

    make CFLAGS+="-traditional-cpp" alt

to do:

    make CC=gcc alt

but still allowing for the former which might be necessary if CC is not
defined to be gcc.

The README.md points out that in macOS gcc is clang.

Improve the command (in the thanks file) of how to see the difference
between the -traditional-cpp version and the fixed version so that it
doesn't need git but rather just diff (as git diff is unnecessary here).
Note that there is discussion about new make rules that will make this
type of thing not needed so the thanks file would be updated at this
point for that to just refer to the FAQ (or not say anything about it at
all).

1986/wall/Makefile

@@ -103,6 +103,7 @@ ifeq ($(CC),gcc)
 #
 #CWARN+=
 #
+CFLAGS+= -traditional-cpp
 endif
 
 
@@ -136,9 +137,12 @@ ${PROG}: ${PROG}.c
 
 # alternative executable
 #
-alt: data ${ALT_TARGET}
+alt: ${ALT_TARGET}
 	@${TRUE}
 
+${PROG}.alt: ${PROG}.alt.c
+	${CC} ${CFLAGS} $< -o $@ ${LDFLAGS}
+
 # data files
 #
 data: ${DATA}

1986/wall/README.md

@@ -26,10 +26,15 @@ might enjoy looking at the original source in [wall.alt.c](wall.alt.c).
 # if you have an old enough compiler:
 make alt
 
-# or with gcc:
+# or if you have gcc:
+make CC=gcc alt
+
+# or if you have a compiler that supports -traditional-cpp that's not gcc:
 make CFLAGS+="-traditional-cpp" alt
 ```
 
+NOTE: gcc in macOS is actually clang even the binary `/usr/bin/gcc`.
+
 Use `./wall.alt` as you would `./wall`.
 
 ## Judges' remarks:

thanks-for-fixes.md

@@ -11,21 +11,22 @@ contributed thousands, that we wish to thank.
 
 We call out the extensive contributions of [Cody Boone
 Ferguson](https://www.ioccc.org/winners.html#Cody_Boone_Ferguson) who is
-responsible for many of the improvements including many, many **very complicated
-bug fixes** ([1988/phillipps](1988/phillipps/README.md),
-[2001/anonymous](2001/anonymous/README.md), [2004/burley](2004/burley/README.md)
-and others) making entries not require `-traditional-cpp` (which are **very
-complicated fixes**), fixing entries to compile with clang, fixing entries to
-work with macOS (some being **very complicated** like
-[1998/schweikh1](1998/schweikh1/README.md)), fixing code to work with both
-32-bit/64-bit which *can be* **very complicated** (like
-[2001/herrmann2](2001/herrmann2/README.md)), providing alternate code where
-useful/necessary, fixing where possible dead links or removing them,
-typo/consistency fixes, improving **ALL _Makefiles_** and writing
-[sgit](https://github.com/xexyl/sgit) that we installed locally and used to
-easily run `sed` on files in the repo to help build the website. **Thank you
-very much** for your extensive efforts in helping improve the IOCCC presentation
-of past IOCCC winners and fixing so many for modern systems!
+responsible for many of the improvements including many **very complicated bug
+fixes** like [1988/phillipps](1988/phillipps/README.md),
+[2001/anonymous](2001/anonymous/README.md) and
+[2004/burley](2004/burley/README.md), making entries like
+[1986/wall](1986/wall/README.md) not require `-traditional-cpp` (all **very
+complicated fixes**), fixing entries to compile with clang, porting entries to
+macOS, some being **very complicated** like
+[1998/schweikh1](1998/schweikh1/README.md), fixing code like
+[2001/herrmann2](2001/herrmann2/README.md) to work in both 32-bit/64-bit which
+*can be* **very complicated**, providing alternate code where useful/necessary,
+fixing where possible dead links or removing them, typo/consistency fixes,
+improving **ALL _Makefiles_** and writing [sgit](https://github.com/xexyl/sgit)
+that we installed locally to easily run `sed` on files in the repo to help build
+the website. **Thank you very much** for your extensive efforts in helping
+improve the IOCCC presentation of past IOCCC winners and fixing almost all for
+modern systems!
 
 [Yusuke Endoh](https://www.ioccc.org/winners.html#Yusuke_Endoh) supplied a
 number of important bug fixes to a number of past IOCCC winners. Some of those
@@ -261,15 +262,16 @@ noted earlier, very complicated, but we encourage you to look at [original
 code](1986/wall/wall.orig.c) to see how different C was in 1986.
 
 Yusuke originally patched this to use `strdup()` on two strings and this let it
-work with gcc but it still requires `-traditional-cpp`. The [alternate
+work with gcc but it still required `-traditional-cpp`. The [alternate
 code](1986/wall/wall.alt.c) is the version patched by Yusuke should you wish to
-try it with a compiler that has the `-traditional-cpp`.
+try it with a compiler that has the `-traditional-cpp`. See the README.md file
+for details.
 
 If you'd like to see the difference between the version that requires
 `-traditional-cpp` and the fixed version, try:
 
 ```sh
-git diff 82cbf069a781d64802fc59b36778c0b02be4043e..a74abb69b7e9b87e305b529941bf46f97ffff341 1986/wall/wall.c
+diff 1986/wall/wall.alt.c 1986/wall/wall.c
 ```
 
 ## [1987/heckbert](1987/heckbert/heckbert.c) ([README.md](1987/heckbert/README.md))