Link curl and the test apps with -lrt explicitly when necessary

When curl calls a function from that library then it needs to
explicitly link to the library instead of piggybacking on
libcurl's own dependency.  Without this, GNU ld with the
--no-add-needed flag fails when linking (which Fedora now does
by default).

Reported by: Quanah Gibson-Mount
Bug: http://curl.haxx.se/mail/lib-2010-09/0085.html

RELEASE-NOTES

@@ -25,6 +25,7 @@ This release includes the following bugfixes:
  o Curl_is_connected: use correct errno
  o Added SSPI build to Watcom makefile
  o progress: callback for POSTs less than MAX_INITIAL_POST_SIZE
+ o linking problem on Fedora 13
 
 This release includes the following known bugs:
 
@@ -34,6 +35,6 @@ This release would not have looked like this without help, code, reports and
 advice from friends like these:
 
  Kamil Dudka, Ben Greear, Cameron Kaiser, Dan Fandrich, Dirk Manske,
- Guenter Knauf, Julien Chaffraix, Kamil Dudka
+ Guenter Knauf, Julien Chaffraix, Kamil Dudka, Quanah Gibson-Mount
 
         Thanks! (and sorry if I forgot to mention someone)

acinclude.m4

@@ -2145,6 +2145,7 @@ AC_DEFUN([CURL_CHECK_LIBS_CLOCK_GETTIME_MONOTONIC], [
         else
           LIBS="$curl_cv_gclk_LIBS $curl_cv_save_LIBS"
         fi
+        CURL_LIBS="$CURL_LIBS $curl_cv_gclk_LIBS"
         AC_MSG_RESULT([$curl_cv_gclk_LIBS])
         ac_cv_func_clock_gettime="yes"
         ;;

tests/libtest/Makefile.am

@@ -54,7 +54,7 @@ EXTRA_DIST = test75.pl test307.pl test610.pl test613.pl test1013.pl	\
 test1022.pl Makefile.inc
 
 # Dependencies (may need to be overriden)
-LDADD = $(top_builddir)/lib/libcurl.la
+LDADD = $(top_builddir)/lib/libcurl.la @CURL_LIBS@
 DEPENDENCIES = $(top_builddir)/lib/libcurl.la
 
 # Makefile.inc provides the source defines (TESTUTIL, SUPPORTFILES,