STYLE: Convert CMake-language commands to lower case

STYLE: Convert CMake-language commands to lower case

Ancient CMake versions required upper-case commands.  Later command
names became case-insensitive.  Now the preferred style is lower-case.

Run the following shell code:
NOTE: MUST USE GNU compliant version of sed

cmake --help-command-list \
| grep -v "cmake version" \
| while read c; do
    echo 's/\b'"$(echo $c | tr '[:lower:]' '[:upper:]')"'\(\s*\)(/'"$c"'\1(/g'
  done >convert.sed \
&& git ls-files -z -- bootstrap '*.cmake' '*.cmake.in' '*CMakeLists.txt' \
   | xargs -0 gsed -i -f convert.sed \
&& rm convert.sed