maint: Clean up m-files to follow Octave coding conventions. Try to trim long lines to < 80 chars. Use '##' for single line comments. Use '(...)' around tests for if/elseif/switch/while. Abut cell indexing operator '{' next to variable. Abut array indexing operator '(' next to variable. Use space between negation operator '!' and following expression. Use two newlines between endfunction and start of %!test or %!demo code. Remove unnecessary parens grouping between short-circuit operators. Remove stray extra spaces (typos) between variables and assignment operators. Remove stray extra spaces from ends of lines.

FCN_FILE_DIRS += testfun

testfun_FCN_FILES = \
  testfun/__have_feature__.m \
  testfun/__printf_assert__.m \
  testfun/__prog_output_assert__.m \
  testfun/__run_test_suite__.m \
  testfun/assert.m \
  testfun/demo.m \
  testfun/example.m \
  testfun/fail.m \
  testfun/rundemos.m \
  testfun/runtests.m \
  testfun/speed.m \
  testfun/test.m

FCN_FILES += $(testfun_FCN_FILES)

PKG_ADD_FILES += testfun/PKG_ADD

DIRSTAMP_FILES += testfun/$(octave_dirstamp)