[PATCH] makefile: hide stderr of curl-config test

Currently, if you don't have curl installed, you will get

    $ make distclean 2>&1 | grep curl
    /bin/sh: curl-config: not found
    /bin/sh: curl-config: not found
    /bin/sh: curl-config: not found
    /bin/sh: curl-config: not found
    /bin/sh: curl-config: not found
    $

The intent is not to alarm the user, but just to test if there is a new enough curl installed. However, if you look at search engine suggested completions, the above "error" messages are confusing people into thinking curl is a hard requirement.

This test dates back 7+ years to:

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  commit 0890098780f295f2a58658d1f6b6627e40426c72
  Author: Nick Hengeveld <nickh@reactrix.com>
  Date:   Fri Nov 18 17:08:36 2005 -0800

    Decide whether to build http-push in the Makefile
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It wants to ensure curl is newer than 070908. The oldest machine I could find (RHEL 4.6) is 2007 vintage according to /proc/version data, and it has curl 070C01.

The failure here is to mask stderr in the test. However, since the chance of curl being installed, but too old is essentially nil, lets just check for existence and drop the ancient version threshold check, if for no other reason, than to simplifly the parsing of what the makefile is trying to do by humans.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>