tls_openssl: removed unused openssl/rand.h
tls_schannel: [style] use LF for EOL, not CR+LF
tls_schannel: [style] removed trailing spaces
autotools: export only public API for dynamic library
sha1: removed xmpp_ prefix from SHA1 symbols

Prefix was introduced in a981c0a as a workaround. Now, non-public API is
not exported, so this patch hides SHA1 symbols for dynamic library.