fix compilation under std=c89

There were few things that prevented successful compilation
using c89 standard. (and other c* standards in case of gcc).
Fix them in this small patch.

Changes in 27/rand.c:
- Use __GNU_SOURCE__ instead of __GNU_LIBRARY__
  or else any of -std=c* options don't work with gcc
- Add a check before using rand_r() as suggested in rand_r(3)
- Move _WIN_32 definitions to "else" branch because it uses the most portable version

AUTHORS

@@ -58,6 +58,7 @@ Thanks to the following people for patches and bug reports:
   * Stephen Lewis
   * Taylor Venable
   * Travis Cross
+  * Vitaliy Mysak
   * Yuki Okumura
 
 If you would prefer not to be listed, or are one of the users listed

bignum.c

@@ -772,10 +772,10 @@ sexp sexp_double_to_ratio (sexp ctx, double f) {
   return res;
 }
 
-//
-// For conversion that does not introduce round-off error,
-// no matter what FLT_RADIX is.
-//
+/*
+ * For conversion that does not introduce round-off error,
+ * no matter what FLT_RADIX is.
+ */
 sexp sexp_double_to_ratio_2 (sexp ctx, double f) {
   int sign,i;
   sexp_gc_var3(res, whole, scale);

lib/srfi/27/rand.c

@@ -18,7 +18,7 @@
 
 #define sexp_sizeof_random (sexp_sizeof_header + sizeof(sexp_random_t) + sizeof(sexp))
 
-#ifdef __GNU_LIBRARY__
+#ifdef __GNU_SOURCE__
 
 typedef struct random_data sexp_random_t;
 
@@ -31,17 +31,7 @@ typedef struct random_data sexp_random_t;
 #define sexp_call_random(rs, dst) random_r(sexp_random_data(rs), &dst)
 #define sexp_seed_random(n, rs) srandom_r(n, sexp_random_data(rs))
 
-#elif defined(_WIN32)
-
-typedef unsigned int sexp_random_t;
-
-/* FIXME: MSVC CRT has rand_s() for "cryptographically secure" random number
- *        for WinXP or later. */
-#define sexp_random_init(rs, seed) (void)0
-#define sexp_call_random(rs, dst) ((dst) = rand())
-#define sexp_seed_random(n, rs) srand(n)
-
-#else
+#elif _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _POSIX_SOURCE
 
 typedef unsigned int sexp_random_t;
 
@@ -50,6 +40,17 @@ typedef unsigned int sexp_random_t;
 #define sexp_call_random(rs, dst) ((dst) = rand_r(sexp_random_data(rs)))
 #define sexp_seed_random(n, rs) *sexp_random_data(rs) = (n)
 
+#else
+
+typedef unsigned int sexp_random_t;
+
+#define sexp_random_init(rs, seed) (void)0
+
+/* FIXME: MSVC CRT has rand_s() for "cryptographically secure" random number
+ *        for WinXP or later. */
+#define sexp_call_random(rs, dst) ((dst) = rand())
+#define sexp_seed_random(n, rs) srand(n)
+
 #endif
 
 sexp sexp_rs_random_integer (sexp ctx, sexp self, sexp_sint_t n, sexp rs, sexp bound) {

sexp.c

@@ -583,7 +583,7 @@ void sexp_init_context_globals (sexp ctx) {
   for (i=0; i<SEXP_NUM_CORE_TYPES; i++) {
     type = sexp_alloc_type(ctx, type, SEXP_TYPE);
     if (!type) {
-      return; // TODO - fundamental OOM, what to do here?
+      return; /* TODO - fundamental OOM, what to do here? */
     }
     memcpy(&(type->value), &(_sexp_type_specs[i]), sizeof(_sexp_type_specs[0]));
     vec[i] = type;