Simplify recursive load

No need to use debugging in this stable feature

src/include/config.sh

     #
     # Find file(s) candidates and load them (or use *__merge)
     #
-    if test -z "$1";
-    then                # guess filename from section head
-        local guess="${wntsct%%.*}$FFOO_CONFIG_SUFFIX"
-        debug -v guess
-        __inigrep__load "$guess"
-    fi
+    test -n "$1" || __inigrep__load "${wntsct%%.*}$FFOO_CONFIG_SUFFIX"
     local arg trydir trypath
     for arg in "$@";
     do