Improve c++ compatibility of htslib header files

Allow room in kputuw_dig2r for the nul byte on the end of the
string used to initialize it.  gcc doesn't mind it being dropped
but g++ complains.

Avoid INTx_MIN, INTx_MAX and SIZE_MAX macros from <stdint.h> in
htslib/*.h header files.  Old versions of glibc (before 2.18), and
possibly other libc implementations don't automatically supply them
when compiling as c++.  Easiest solution is to not use them in
these headers.
(See https://sourceware.org/bugzilla/show_bug.cgi?id=15366)

Fixes #771 (kstring.h error: initializer-string for array of chars
is too long)

htslib/kstring.h

@@ -151,7 +151,8 @@ static inline char *ks_release(kstring_t *s)
 
 static inline int kputsn(const char *p, size_t l, kstring_t *s)
 {
-    if (l > SIZE_MAX - 2 - s->l || ks_resize(s, s->l + l + 2) < 0)
+	size_t new_sz = s->l + l + 2;
+	if (new_sz < s->l || ks_resize(s, new_sz) < 0)
 		return EOF;
 	memcpy(s->s + s->l, p, l);
 	s->l += l;
@@ -183,7 +184,8 @@ static inline int kputc_(int c, kstring_t *s)
 
 static inline int kputsn_(const void *p, size_t l, kstring_t *s)
 {
-	if (l > SIZE_MAX - s->l || ks_resize(s, s->l + l) < 0)
+	size_t new_sz = s->l + l;
+	if (new_sz < s->l || ks_resize(s, new_sz) < 0)
 		return EOF;
 	memcpy(s->s + s->l, p, l);
 	s->l += l;
@@ -208,7 +210,7 @@ static inline int kputuw(unsigned x, kstring_t *s)
 #else
     uint64_t m;
 #endif
-    static const char kputuw_dig2r[200] =
+    static const char kputuw_dig2r[] =
         "00010203040506070809"
         "10111213141516171819"
         "20212223242526272829"

htslib/vcf.h

@@ -876,14 +876,25 @@ typedef struct {
     enables to handle correctly vectors with different ploidy in presence of
     missing values.
  */
-#define bcf_int8_vector_end  (INT8_MIN+1)
-#define bcf_int16_vector_end (INT16_MIN+1)
-#define bcf_int32_vector_end (INT32_MIN+1)
+#define bcf_int8_vector_end  (-127)         /* INT8_MIN  + 1 */
+#define bcf_int16_vector_end (-32767)       /* INT16_MIN + 1 */
+#define bcf_int32_vector_end (-2147483647)  /* INT32_MIN + 1 */
 #define bcf_str_vector_end   0
-#define bcf_int8_missing     INT8_MIN
-#define bcf_int16_missing    INT16_MIN
-#define bcf_int32_missing    INT32_MIN
+#define bcf_int8_missing     (-128)          /* INT8_MIN  */
+#define bcf_int16_missing    (-32767-1)      /* INT16_MIN */
+#define bcf_int32_missing    (-2147483647-1) /* INT32_MIN */
 #define bcf_str_missing      0x07
+
+// Limits on BCF values stored in given types.  Max values are the same
+// as for the underlying type.  Min values are slightly different as
+// the last 8 values for each type were reserved by BCFv2.2.
+#define BCF_MAX_BT_INT8  (0x7f)        /* INT8_MAX  */
+#define BCF_MAX_BT_INT16 (0x7fff)      /* INT16_MAX */
+#define BCF_MAX_BT_INT32 (0x7fffffff)  /* INT32_MAX */
+#define BCF_MIN_BT_INT8  (-120)        /* INT8_MIN  + 8 */
+#define BCF_MIN_BT_INT16 (-32760)      /* INT16_MIN + 8 */
+#define BCF_MIN_BT_INT32 (-2147483640) /* INT32_MIN + 8 */
+
 extern uint32_t bcf_float_vector_end;
 extern uint32_t bcf_float_missing;
 static inline void bcf_float_set(float *ptr, uint32_t value)
@@ -953,8 +964,8 @@ static inline void bcf_enc_size(kstring_t *s, int size, int type)
 
 static inline int bcf_enc_inttype(long x)
 {
-    if (x <= INT8_MAX && x >= INT8_MIN + 8) return BCF_BT_INT8;
-    if (x <= INT16_MAX && x >= INT16_MIN + 8) return BCF_BT_INT16;
+    if (x <= BCF_MAX_BT_INT8 && x >= BCF_MIN_BT_INT8) return BCF_BT_INT8;
+    if (x <= BCF_MAX_BT_INT16 && x >= BCF_MIN_BT_INT16) return BCF_BT_INT16;
     return BCF_BT_INT32;
 }
 
@@ -966,10 +977,10 @@ static inline void bcf_enc_int1(kstring_t *s, int32_t x)
     } else if (x == bcf_int32_missing) {
         bcf_enc_size(s, 1, BCF_BT_INT8);
         kputc(bcf_int8_missing, s);
-    } else if (x <= INT8_MAX && x >= INT8_MIN + 8) {
+    } else if (x <= BCF_MAX_BT_INT8 && x >= BCF_MIN_BT_INT8) {
         bcf_enc_size(s, 1, BCF_BT_INT8);
         kputc(x, s);
-    } else if (x <= INT16_MAX && x >= INT16_MIN + 8) {
+    } else if (x <= BCF_MAX_BT_INT16 && x >= BCF_MIN_BT_INT16) {
         int16_t z = x;
         bcf_enc_size(s, 1, BCF_BT_INT16);
         kputsn((char*)&z, 2, s);