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

Command copied from http://cmake.org/gitweb?p=cmake.git;a=commit;h=77543bde
Remove explicit declaration of BUILD_TESTING option

Including the CTest module is sufficient to add the option BUILD_TESTING
with default value set to ON.

See http://www.cmake.org/cmake/help/v2.8.2/cmake.html#module:CTest
Simplify how additional C/CXX flags can be specified

Since CMake already provide a way to specify additional compiler flags
setting the CFLAGS and CXXFLAGS environment variables, this commit
remove the redundant "ADDITIONAL_(C|CXX)_FLAGS" CMake options.