Add opt.experimental_infallible_new.

This allows a guarantee that operator new never throws.

Fix the .gitignore rules to include test/integration/cpp while we're here.

include/jemalloc/internal/jemalloc_internal_defs.h.in

@@ -401,6 +401,9 @@
 /* Performs additional safety checks when defined. */
 #undef JEMALLOC_OPT_SAFETY_CHECKS
 
+/* Is C++ support being built? */
+#undef JEMALLOC_ENABLE_CXX
+
 /* Performs additional size checks when defined. */
 #undef JEMALLOC_OPT_SIZE_CHECKS
 

include/jemalloc/internal/jemalloc_internal_externs.h

@@ -26,6 +26,7 @@ extern void (*junk_free_callback)(void *ptr, size_t size);
 extern void (*junk_alloc_callback)(void *ptr, size_t size);
 extern bool opt_utrace;
 extern bool opt_xmalloc;
+extern bool opt_experimental_infallible_new;
 extern bool opt_zero;
 extern unsigned opt_narenas;
 extern zero_realloc_action_t opt_zero_realloc_action;

include/jemalloc/internal/jemalloc_preamble.h.in

@@ -198,6 +198,15 @@ static const bool config_opt_size_checks =
 #endif
     ;
 
+/* Whether or not the C++ extensions are enabled. */
+static const bool config_enable_cxx =
+#ifdef JEMALLOC_ENABLE_CXX
+    true
+#else
+    false
+#endif
+;
+
 #if defined(_WIN32) || defined(JEMALLOC_HAVE_SCHED_GETCPU)
 /* Currently percpu_arena depends on sched_getcpu. */
 #define JEMALLOC_PERCPU_ARENA