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.

This is dodgy.
What -D/-I flags for OpenSSL does it make sense to pass to the C linker and compiler, but not to the C preprocessor ?
Is ENTERPRISE_CFLAGS mis-named ?  If so, why not fix it to ENTERPRISE_CPPFLAGS ?
Flags for the preprocessor should go in *CPPFLAGS variables, flags for the linker and compiler in *CFLAGS.