Added function check and declaration for hstrerror.

On FreeBSD-10.1, function hstrerror is implemented in libc but its
declaration is disabled in netdb.h by default. Thus error "implicit
declaration of function hstrerrori" was reported when compiling hydra.
This patch adds two steps in hydra configure in order to transparently
fix this issue:
1. Check if function hstrerror exists (in libc).
2. Add the declaration of hstrerror if it exists in libc but the
declaration is disabled.
Signed-off-by: Pavan Balaji <balaji@anl.gov>

src/pm/hydra/configure.ac

@@ -169,7 +169,11 @@ AC_SEARCH_LIBS(hstrerror, resolv,)
 # Check for necessary functions
 AC_CHECK_FUNCS(gettimeofday time strdup sigaction signal usleep alloca unsetenv \
 	       strerror strsignal stat fcntl alarm isatty inet_ntop getpgid \
-	       setsid killpg)
+	       setsid killpg hstrerror)
+
+if test "$ac_cv_func_hstrerror" = "yes" ; then
+   PAC_FUNC_NEEDS_DECL([#include <netdb.h>],hstrerror)
+fi
 
 if test "$ac_cv_func_gettimeofday" = "yes" ; then
    PAC_FUNC_NEEDS_DECL([#include <sys/time.h>],gettimeofday)

src/pm/hydra/include/hydra.h

@@ -157,6 +157,10 @@ extern char *HYD_dbg_prefix;
 extern char **environ;
 #endif /* MANUAL_EXTERN_ENVIRON */
 
+#if defined NEEDS_HSTRERROR_DECL
+const char * hstrerror(int err);
+#endif /* NEEDS_HSTRERROR_DECL */
+
 #if defined NEEDS_GETTIMEOFDAY_DECL
 int gettimeofday(struct timeval *tv, struct timezone *tz);
 #endif /* NEEDS_GETTIMEOFDAY_DECL */