gl_LIBSIGSEGV is broken

[Sam Steingold]

I just upgraded clisp to libsigsegv.m4 serial 4 and now LIBSIGSEGV is not set 
right:

config.status:
before:
$ grep -i sigsegv config.status
S["LIBSIGSEGV"]="-lsigsegv"
S["LTLIBSIGSEGV"]="-lsigsegv"
D["HAVE_LIBSIGSEGV"]=" 1"
D["HAVE_LIBSIGSEGV"]=" 1"

after:
$ grep -i sigsegv config.status
S["LIBSIGSEGV_PREFIX"]=""
S["LTLIBSIGSEGV"]=""
S["LIBSIGSEGV"]=""
S["HAVE_LIBSIGSEGV"]="yes"
D["HAVE_LIBSIGSEGV"]=" 1"
D["HAVE_LIBSIGSEGV"]=" 1"

libsigsegv is installed system-wide (in /usr).