Save literal value of the parsed number to preserve it for the output

Extend jv_number to use decNumber for storing number literals. Any math
operations on the numbers will truncate them to double precision.
Comparisons when both numbers are literal numbers will compare them
without truncation.

Delay conversion of numbers to doubles until a math operation is performed,
to preserve precision. A literal jv_number will only need conversion to
double once, and will reuse the resultant double on subsequent
conversions.

Outputting literal jv_numbers preserves the original precision.

Add strong pthread requirement to manage contexts/allocations for
converting numbers between their decNumber, string, and double formats.

src/builtin.c

@@ -90,8 +90,11 @@ static jv f_plus(jq_state *jq, jv input, jv a, jv b) {
     jv_free(b);
     return a;
   } else if (jv_get_kind(a) == JV_KIND_NUMBER && jv_get_kind(b) == JV_KIND_NUMBER) {
-    return jv_number(jv_number_value(a) +
+    jv r = jv_number(jv_number_value(a) +
                      jv_number_value(b));
+    jv_free(a);
+    jv_free(b);
+    return r;
   } else if (jv_get_kind(a) == JV_KIND_STRING && jv_get_kind(b) == JV_KIND_STRING) {
     return jv_string_concat(a, b);
   } else if (jv_get_kind(a) == JV_KIND_ARRAY && jv_get_kind(b) == JV_KIND_ARRAY) {
@@ -274,7 +277,10 @@ static jv f_rtrimstr(jq_state *jq, jv input, jv right) {
 static jv f_minus(jq_state *jq, jv input, jv a, jv b) {
   jv_free(input);
   if (jv_get_kind(a) == JV_KIND_NUMBER && jv_get_kind(b) == JV_KIND_NUMBER) {
-    return jv_number(jv_number_value(a) - jv_number_value(b));
+    jv r = jv_number(jv_number_value(a) - jv_number_value(b));
+    jv_free(a);
+    jv_free(b);
+    return r;
   } else if (jv_get_kind(a) == JV_KIND_ARRAY && jv_get_kind(b) == JV_KIND_ARRAY) {
     jv out = jv_array();
     jv_array_foreach(a, i, x) {
@@ -302,7 +308,10 @@ static jv f_multiply(jq_state *jq, jv input, jv a, jv b) {
   jv_kind bk = jv_get_kind(b);
   jv_free(input);
   if (ak == JV_KIND_NUMBER && bk == JV_KIND_NUMBER) {
-    return jv_number(jv_number_value(a) * jv_number_value(b));
+    jv r = jv_number(jv_number_value(a) * jv_number_value(b));
+    jv_free(a);
+    jv_free(b);
+    return r;
   } else if ((ak == JV_KIND_STRING && bk == JV_KIND_NUMBER) ||
              (ak == JV_KIND_NUMBER && bk == JV_KIND_STRING)) {
     jv str = a;
@@ -336,7 +345,10 @@ static jv f_divide(jq_state *jq, jv input, jv a, jv b) {
   if (jv_get_kind(a) == JV_KIND_NUMBER && jv_get_kind(b) == JV_KIND_NUMBER) {
     if (jv_number_value(b) == 0.0)
       return type_error2(a, b, "cannot be divided because the divisor is zero");
-    return jv_number(jv_number_value(a) / jv_number_value(b));
+    jv r = jv_number(jv_number_value(a) / jv_number_value(b));
+    jv_free(a);
+    jv_free(b);
+    return r;
   } else if (jv_get_kind(a) == JV_KIND_STRING && jv_get_kind(b) == JV_KIND_STRING) {
     return jv_string_split(a, b);
   } else {
@@ -349,7 +361,10 @@ static jv f_mod(jq_state *jq, jv input, jv a, jv b) {
   if (jv_get_kind(a) == JV_KIND_NUMBER && jv_get_kind(b) == JV_KIND_NUMBER) {
     if ((intmax_t)jv_number_value(b) == 0)
       return type_error2(a, b, "cannot be divided (remainder) because the divisor is zero");
-    return jv_number((intmax_t)jv_number_value(a) % (intmax_t)jv_number_value(b));
+    jv r = jv_number((intmax_t)jv_number_value(a) % (intmax_t)jv_number_value(b));
+    jv_free(a);
+    jv_free(b);
+    return r;
   } else {
     return type_error2(a, b, "cannot be divided (remainder)");
   }
@@ -440,7 +455,9 @@ static jv f_length(jq_state *jq, jv input) {
   } else if (jv_get_kind(input) == JV_KIND_STRING) {
     return jv_number(jv_string_length_codepoints(input));
   } else if (jv_get_kind(input) == JV_KIND_NUMBER) {
-    return jv_number(fabs(jv_number_value(input)));
+    jv r = jv_number(fabs(jv_number_value(input)));
+    jv_free(input);
+    return r;
   } else if (jv_get_kind(input) == JV_KIND_NULL) {
     jv_free(input);
     return jv_number(0);