Remove using std.
cosmetics: add new lines at the end of files.
Don't use camelcase words in About dialog anymore.
contrib/checkyear.sh: include pl files in the check.
Bump copyright year for modified files.

Everyone with push rights has to use the precommit hook.

(Hint: `cp contrib/checkyear.sh .git/hooks/pre-commit`)
Use `#pragma warning(push/pop)` instead of `#pragma warning(default)`.
Simplify preprocessor config.
AudioSwitcher: Fix the initialization of the normalization factor.
AudioSwitcher: Use the defines for the max and min values of a 24-bit integer.
BaseSplitterFileEx: Fix an incorrect check.
BaseSplitterFileEx: Simplify a check.
BufferFilter: Check for null pointers before actually using them.
ComPropertySheet: Remove a redundant check.
FGManagerBDA: Check for null pointer before actually using it.
IPinHook: Fix wrong sizeof.
OpenFileDlg: Avoid creating an empty CPath object.
SubtitleDlDlg: Controls handles aren't initialized yet in the constructor.
STS: Code simplification.