protocol: Correct grammar and spelling

Fix grammar, spelling, tense, and other inconsistencies, based on
correctness, consistency, and precedence both here and influenced
by wayland-protocols.

- Standardize lower case for summary attribute values.
- Minor vertical whitespace removal consistency.
- Standarize references to coordinates, preferring 'surface local'
- Fix spelling, grammar, tense, and punctuation.

Signed-off-by: Yong Bakos <ybakos@humanoriented.com>