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.

Thanks for bringing this up. I'm keeping it as it was for now, I've had enough autoconf-madness in one week. For future reference, this might help for resolving it correctly, from [AC_PROG_CC manual page](https://www.gnu.org/savannah-checkouts/gnu/autoconf/manual/autoconf-2.69/html_node/C-Compiler.html):
> If output variable CFLAGS was not already set, set it to -g -O2 for the GNU C compiler (-O2 on systems where GCC does not accept -g), or -g for other compilers. If your package does not like this default, then it is acceptable to insert the line ‘: ${CFLAGS=""}’ after AC_INIT and before AC_PROG_CC to select an empty default instead.