build: Add deprecation infrastructure back in

This reverts commit 8b7ecc9d646a58d86b38c7b0f943778f766a2995.

Conflicts:
	src/Makefile.am
	src/vte.h
docs: Remove version markers

0.38 has a new API/ABI, so the Since: markers really aren't appropriate.
widget: Deprecated vte_terminal_match_set_cursor

The cursor is specific to a display, and can't be changed when the widget's
display changes. Use a GdkCursorType or named cursor instead.
docs: Add index for API new in 0.40
widget: Check cursor's display before using it