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>
cmake: use LIBCURL_VERSION from curlver.h

This matches the behavior from autotools. The auxiliary major, minor
and patch components are not needed anymore and therefore removed.

Signed-off-by: Peter Wu <peter@lekensteyn.nl>
cmake: generate pkg-config and curl-config

Initial work to generate a pkg-config and curl-config script. Static
linking (`curl-config --static-libs` and `pkg-config --shared --libs
libcurl`) is broken and therefore disabled.

CONFIGURE_OPTIONS does not make sense for CMake, use an empty string
for now.

At least `curl-config --features` and `curl-config --protocols` work
which is needed by runtests.pl.

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