Rename member variable "n" to "len"

Describes the _length_ of the array, not the number of elements.
Rename member variable "next" to "num"

Describes the number of elements of the object.
Fix variable name for command number in processor code
Fix variable names in tests
Merge pull request #329 from matthiasbeyer/fix-variable_names_transaction

Fix variable names in transaction type
Fix callback names
Whitespace cleanup in compositor/buffer/frame.c
Add comments in compositor/buffer/image.c
Whitespace after a cast is good!
Whitespace cleanup in compositor/cursor.c
Fix comment: This is not a doxygen comment
Remove prefix from static functions
Resort function

This patch resorts the functions to be in the right section (interface
implementation vs. internal stuff).
Add section comments in compositor/monitor_mode.c
Added missing "static" keywords
Whitespace cleanup in compositor/wayland/pointer.c
Add missing section comments in compositor/wayland/seat.c
Add missing "static" keyword
Move static function definition to appropriate section
Fix line length violations in sf_commit_blit()