fix(peg): use GC allocated slice instead of always alloca on stack

On big `or!()` templates stack size can grow pretty fast, specially when
recursion is done on similar templates and recursive tail call
optimizations are not possible.

For performance, LDC compiler already optimizes these calls into
stack-based variables when they are too small. Regardless, this library
heavily uses GC on the inner strings, so the impact is negligable.

Author: ljmf00-wekaio

pegged/peg.d

@@ -1664,9 +1664,9 @@ template or(rules...) if (rules.length > 0)
         size_t errorStringChars;
         string orErrorString;
 
-        ParseTree[rules.length] results;
-        string[rules.length] names;
-        size_t[rules.length] failedLength;
+        ParseTree[] results = new ParseTree[rules.length];
+        string[] names = new string[rules.length];
+        size_t[] failedLength = new size_t[rules.length];
         size_t maxFailedLength;
 
         version (tracer)
@@ -1858,9 +1858,9 @@ template longest_match(rules...) if (rules.length > 0)
         size_t errorStringChars;
         string orErrorString;
 
-        ParseTree[rules.length] results;
-        string[rules.length] names;
-        size_t[rules.length] failedLength;
+        ParseTree[] results = new ParseTree[rules.length];
+        string[] names = new string[rules.length];
+        size_t[] failedLength = new size_t[rules.length];
         size_t maxFailedLength;
 
         version (tracer)