Header refactoring: Split up jemalloc_internal.h

This is a biggy.  jemalloc_internal.h has been doing multiple jobs for a while
now:
- The source of system-wide definitions.
- The catch-all include file.
- The module header file for jemalloc.c

This commit splits up this functionality.  The system-wide definitions
responsibility has moved to jemalloc_preamble.h.  The catch-all include file is
now jemalloc_internal_includes.h.  The module headers for jemalloc.c are now in
jemalloc_internal_[externs|inlines|types].h, just as they are for the other
modules.

include/jemalloc/internal/jemalloc_internal_externs.h

@@ -0,0 +1,61 @@
+#ifndef JEMALLOC_INTERNAL_EXTERNS_H
+#define JEMALLOC_INTERNAL_EXTERNS_H
+
+extern bool	opt_abort;
+extern const char	*opt_junk;
+extern bool	opt_junk_alloc;
+extern bool	opt_junk_free;
+extern bool	opt_utrace;
+extern bool	opt_xmalloc;
+extern bool	opt_zero;
+extern unsigned	opt_narenas;
+
+/* Number of CPUs. */
+extern unsigned	ncpus;
+
+/* Number of arenas used for automatic multiplexing of threads and arenas. */
+extern unsigned	narenas_auto;
+
+/*
+ * Arenas that are used to service external requests.  Not all elements of the
+ * arenas array are necessarily used; arenas are created lazily as needed.
+ */
+extern atomic_p_t arenas[];
+
+/*
+ * pind2sz_tab encodes the same information as could be computed by
+ * pind2sz_compute().
+ */
+extern size_t const	pind2sz_tab[NPSIZES+1];
+/*
+ * index2size_tab encodes the same information as could be computed (at
+ * unacceptable cost in some code paths) by index2size_compute().
+ */
+extern size_t const	index2size_tab[NSIZES];
+/*
+ * size2index_tab is a compact lookup table that rounds request sizes up to
+ * size classes.  In order to reduce cache footprint, the table is compressed,
+ * and all accesses are via size2index().
+ */
+extern uint8_t const	size2index_tab[];
+
+void *a0malloc(size_t size);
+void a0dalloc(void *ptr);
+void *bootstrap_malloc(size_t size);
+void *bootstrap_calloc(size_t num, size_t size);
+void bootstrap_free(void *ptr);
+void arena_set(unsigned ind, arena_t *arena);
+unsigned narenas_total_get(void);
+arena_t *arena_init(tsdn_t *tsdn, unsigned ind, extent_hooks_t *extent_hooks);
+arena_tdata_t *arena_tdata_get_hard(tsd_t *tsd, unsigned ind);
+arena_t *arena_choose_hard(tsd_t *tsd, bool internal);
+void arena_migrate(tsd_t *tsd, unsigned oldind, unsigned newind);
+void iarena_cleanup(tsd_t *tsd);
+void arena_cleanup(tsd_t *tsd);
+void arenas_tdata_cleanup(tsd_t *tsd);
+void jemalloc_prefork(void);
+void jemalloc_postfork_parent(void);
+void jemalloc_postfork_child(void);
+bool malloc_initialized(void);
+
+#endif /* JEMALLOC_INTERNAL_EXTERNS_H */