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:

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' |
egrep -z -v '^(Utilities/cm|Source/kwsys/)' |
xargs -0 sed -i -f convert.sed &&
rm convert.sed

Modules/FindOpenSceneGraph.cmake

@@ -161,7 +161,7 @@ if(OpenSceneGraph_FIND_QUIETLY)
     set(_osg_quiet "QUIET")
 endif()
 #
-# Here we call FIND_PACKAGE() on all of the components
+# Here we call find_package() on all of the components
 #
 foreach(_osg_module ${_osg_modules_to_process})
     if(OpenSceneGraph_DEBUG)