Fix a few cmake configure-time checks.

A couple of actual checks were missing (elf_aux_info, sysctlbyname).
Several more were accidentally left out of cmake.h.in, meaning they
wouldn't be propagated from cmake's variable space into the actual
compilation. And a handful of checks in the C source were still using
the autotools-style 'if defined' in place of the cmake-style "it's
always 0 or 1" plain #if.

unix/uxmisc.c

@@ -24,7 +24,7 @@ unsigned long getticks(void)
      * need a decent number of them to fit into a 32-bit word so it
      * can be used for keepalives.
      */
-#if defined HAVE_CLOCK_GETTIME && defined HAVE_DECL_CLOCK_MONOTONIC
+#if HAVE_CLOCK_GETTIME && HAVE_CLOCK_MONOTONIC
     {
         /* Use CLOCK_MONOTONIC if available, so as to be unconfused if
          * the system clock changes. */

unix/uxutils.h

@@ -30,9 +30,9 @@
 #include <asm/hwcap.h>
 #endif
 
-#if defined HAVE_GETAUXVAL
+#if HAVE_GETAUXVAL
 /* No code needed: getauxval has just the API we want already */
-#elif defined HAVE_ELF_AUX_INFO
+#elif HAVE_ELF_AUX_INFO
 /* Implement the simple getauxval API in terms of FreeBSD elf_aux_info */
 static inline u_long getauxval(int which)
 {