Correct comments in testdir makefiles. (John Beckett)

src/testdir/Make_amiga.mak

 #
-# Makefile to run al tests for Vim, on Amiga
+# Makefile to run all tests for Vim, on Amiga
 #
 # Requires "rm", "csh" and "diff"!
 

src/testdir/Make_dos.mak

 #
-# Makefile to run al tests for Vim, on Dos-like machines.
+# Makefile to run all tests for Vim, on Dos-like machines.
 #
 # Requires a set of Unix tools: echo, diff, etc.
 

src/testdir/Make_ming.mak

-# Makefile to run tests for Vim, on Dos-like machines
+#
+# Makefile to run all tests for Vim, on Dos-like machines
 # with sh.exe or zsh.exe in the path or not.
 #
 # Author: Bill McCarthy

src/testdir/Make_os2.mak

 #
-# Makefile to run al tests for Vim, on OS/2
+# Makefile to run all tests for Vim, on OS/2
 #
 # Requires a set of Unix tools: echo, diff, etc.
 

src/testdir/main.aap

 #
-# Makefile to run al tests for Vim
+# Makefile to run all tests for Vim
 #
 
 VimProg ?= ../vim