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.

tests/jq.test

@@ -1673,3 +1673,42 @@ false
 #null
 
 
+#
+# Tests to cover the new toliteral number functionality
+# For an example see #1652 and other linked issues
+#
+
+# We are backward and sanity compatible
+
+map(. == 1)
+[1, 1.0, 1.000, 100e-2, 1e+0, 0.0001e4]
+[true, true, true, true, true, true]
+
+# When no arithmetic is involved jq should preserve the literal value
+
+.[0] | tostring
+[13911860366432393]
+"13911860366432393"
+
+.x | tojson
+{"x":13911860366432393}
+"13911860366432393"
+
+13911860366432393 == 13911860366432392
+null
+false
+
+
+# Applying arithmetic to the value will truncate the result to double
+
+. - 10
+13911860366432393
+13911860366432382
+
+.[0] - 10
+[13911860366432393]
+13911860366432382
+
+.x - 10
+{"x":13911860366432393}
+13911860366432382

tests/local.supp

@@ -0,0 +1,14 @@
+{
+   macos valgrind 1
+   Memcheck:Leak
+   match-leak-kinds: possible
+   fun:calloc
+   fun:map_images_nolock
+   ...
+   fun:_dyld_objc_notify_register
+   fun:_objc_init
+   fun:_os_object_init
+   fun:libdispatch_init
+   fun:libSystem_initializer
+   ...
+}

tests/setup

@@ -14,7 +14,8 @@ JQ=$JQBASEDIR/jq
 
 if [ -z "${NO_VALGRIND-}" ] && which valgrind > /dev/null; then
     VALGRIND="valgrind --error-exitcode=1 --leak-check=full \
-                       --suppressions=$JQTESTDIR/onig.supp"
+                       --suppressions=$JQTESTDIR/onig.supp \
+                       --suppressions=$JQTESTDIR/local.supp"
     VG_EXIT0=--error-exitcode=0
     Q=-q
 else