Add a missing strtol() family test and a hex benchmark.

Benchmark added to test an optimization I'll send round next, test added
when an even bigger refactoring (as part of a more interesting
optimization) broke strtol() in a way the strtol() tests didn't notice.

Test: treehugger
Change-Id: Ic974900021107938dbbbe98648960adb102d9595
diff --git a/benchmarks/stdlib_benchmark.cpp b/benchmarks/stdlib_benchmark.cpp
index 9be72e7..7680b40 100644
--- a/benchmarks/stdlib_benchmark.cpp
+++ b/benchmarks/stdlib_benchmark.cpp
@@ -235,3 +235,6 @@
 BIONIC_TRIVIAL_BENCHMARK(BM_stdlib_strtoll, strtoll(" -123", nullptr, 0));
 BIONIC_TRIVIAL_BENCHMARK(BM_stdlib_strtoul, strtoul(" -123", nullptr, 0));
 BIONIC_TRIVIAL_BENCHMARK(BM_stdlib_strtoull, strtoull(" -123", nullptr, 0));
+
+BIONIC_TRIVIAL_BENCHMARK(BM_stdlib_strtol_hex, strtol("0xdeadbeef", nullptr, 0));
+BIONIC_TRIVIAL_BENCHMARK(BM_stdlib_strtoul_hex, strtoul("0xdeadbeef", nullptr, 0));