Almost all the CMake options begin with LWS_WITH_..., but many of the
symbols passed to lws are LWS_USE_... , this causes neededless confusion,
compounded by the fact that a few CMake options also begin with
LWS_USE_.
This patch globally converts all LWS_USE_... to LWS_WITH_..., so there
is only one prefix to remember in both CMake and the code.
The affected public CMake options are
LWS_USE_BORINGSSL -> LWS_WITH_BORINGSSL
LWS_USE_CYASSL -> LWS_WITH_CYASSL
LWS_USE_WOLFSSL -> LWS_WITH_WOLFSSL
LWS_USE_MBEDTLS -> LWS_WITH_MBEDTLS
LWS_USE_BUNDLED_ZLIB -> LWS_WITH_BUNDLED_ZLIB
1) There's now a .fops pointer that can be set in the context creation info. If set, the array of
fops it points to (terminated by an entry with .open = NULL) is walked to find out the best vfs filesystem
path match (comparing the vfs path to fops.path_prefix) for which fops to use.
If none given (.fops is NULL in info) then behaviour is as before, fops are the platform-provided one only.
2) The built in fileserving now walks any array of fops looking for the best fops match automatically.
3) lws_plat_file_... apis are renamed to lws_vfs_file_...
