This avoids redundant "if (x == NULL)" style checks and puts the onus on
the caller to use valid parameters.

Also added whitespace checking pre-commit hook when autogen.sh is called.

This avoids casts and is cleaner.

No need to represent DTMF with an enum

99 % of these are just whitespace changes. Some unnecessary includes
removed as well

Found with -Wshadow argument to g++