cmake: add SUPPORT_FEATURES and SUPPORT_PROTOCOLS

For compatibility with autoconf, it will be used later for curl-config
and pkg-config. Not all features and or protocols can be enabled as
these are missing additional checks (see new TODOs).

SUPPORT_PROTOCOLS is partially scripted (grep for SUPPORT_PROTOCOLS=)
and manually verified/modified. SUPPORT_FEATURES is manually added.

Signed-off-by: Peter Wu <peter@lekensteyn.nl>