Automake sanitisation

    Do not alter environment CFLAGS, CPPFLAGS etc.
    
    These variables should never be overriden by our makefiles, only the
    AM_CFLAGS or libcf_agent_la_CFLAGS variants are to be set.
    
    Also fixed wrong libutils dependencies that were discovered after this
    change: libutils currently must link to OpenSSL and PCRE.
    
    This clean-up occurred after an attempt to only link cf-upgrade to
    libutils, but noticing that it pulls out everything as dependency.

autoconf never messes with CFLAGS AFAIK. CFLAGS come strictly from the environment (and maybe from m4 macros that are buggy and indeed mess them up). The whole spirit of this change is to ensure that CFLAGS are from the environment, no EVN_CFLAGS should be needed.