Update 2020 MANIFEST

Fixed references to files that no longer exist (were renamed).

2020/MANIFEST

@@ -36,12 +36,12 @@
 2020/ferguson1/COMPILING
 2020/ferguson1/HACKING
 2020/ferguson1/Makefile
-2020/ferguson1/bugs.text
+2020/ferguson1/bugs.md
 2020/ferguson1/cake.jpg
 2020/ferguson1/cannibalism.log
-2020/ferguson1/chocolate-cake.text
+2020/ferguson1/chocolate-cake.md
 2020/ferguson1/crazy.log
-2020/ferguson1/gameplay.text
+2020/ferguson1/gameplay.md
 2020/ferguson1/halfwidth_vs_fullwidth.png
 2020/ferguson1/README.md
 2020/ferguson1/ioccc-cake.jpg
@@ -53,24 +53,24 @@
 2020/ferguson1/prog.c
 2020/ferguson1/snake-colours.sh
 2020/ferguson1/snake.1
-2020/ferguson1/spoilers.text
+2020/ferguson1/spoilers.md
 2020/ferguson1/termcaps.c
-2020/ferguson1/terminals.text
-2020/ferguson1/troubleshooting.text
+2020/ferguson1/terminals.md
+2020/ferguson1/troubleshooting.md
 2020/ferguson2/Makefile
 2020/ferguson2/cake.jpg
-2020/ferguson2/chocolate-cake.text
+2020/ferguson2/chocolate-cake.md
 2020/ferguson2/enigma.1
 2020/ferguson2/README.md
 2020/ferguson2/input.txt
 2020/ferguson2/ioccc-cake.jpg
 2020/ferguson2/obfuscation.key
-2020/ferguson2/obfuscation.text
+2020/ferguson2/obfuscation.md
 2020/ferguson2/obfuscation.txt
 2020/ferguson2/prog.c
 2020/ferguson2/recode.1
 2020/ferguson2/recode.c
-2020/ferguson2/recode.text
+2020/ferguson2/recode.md
 2020/ferguson2/try.this.txt
 2020/giles/Makefile
 2020/giles/dtmf.bin