Add benchmarks

One of the benchmarks is generated. It may be useful to do that
sometimes, especially with parser-oriented benchmarks. Jsonnet
is used to generate the 5th benchmark (dogfooding!).

*.gen.jsonnet files are added to local .gitignore so that we don't
keep big benchmarks in the repo. Run ./regen_benchmarks.sh to generate
them.

Author: sbarzowski

benchmarks/.gitignore

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+*.gen.jsonnet

benchmarks/bench.04.jsonnet

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+std.foldl(function(e, res) e + res, std.makeArray(20000, function(i) 'aaaaa'), '')

benchmarks/bench.07.jsonnet

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+local f2(f) = function(x) f(f(x));
+local id(x) = x;
+
+local slowId = std.makeArray(20, function(i) if i == 0 then id else f2(slowId[i - 1]));
+
+slowId[15](42)

benchmarks/gen_big_object.jsonnet

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+local n = 2000;
+
+local objLocal(name, body) = 'local ' + name + ' = ' + body + ',';
+local objField(name, body) = name + ': ' + body + ',';
+
+local allLocals =
+  std.makeArray(n, function(i) objLocal('l' + i, '1'));
+
+local allFields =
+  std.makeArray(n, function(i) objField('f' + i, '2'));
+
+local indent = '  ';
+local indentAndSeparate(s) = indent + s + '\n';
+
+local objContents = std.map(indentAndSeparate, allLocals + allFields);
+
+local objectBody = std.join('', objContents);
+'{\n' + objectBody + '}\n'

benchmarks/regen_benchmarks.sh

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+#!/bin/bash
+
+set -e
+set -x
+
+../jsonnet -S gen_big_object.jsonnet > bench.05.gen.jsonnet
+
+for i in *.gen.jsonnet; do
+	../jsonnet fmt -i "$i"
+done