Fix a regression in JE_COMPILABLE().

Revert JE_COMPILABLE() so that it detects link errors.  Cross-compiling
should still work as long as a valid configure cache is provided.

Clean up some comments/whitespace.

configure.ac

@@ -26,11 +26,14 @@ AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
 ])
 
 dnl JE_COMPILABLE(label, hcode, mcode, rvar)
+dnl 
+dnl Use AC_RUN_IFELSE() rather than AC_COMPILE_IFELSE() so that linker errors
+dnl cause failure.
 AC_DEFUN([JE_COMPILABLE],
 [
 AC_CACHE_CHECK([whether $1 is compilable],
                [$4],
-               [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([$2],
+               [AC_RUN_IFELSE([AC_LANG_PROGRAM([$2],
                                                [$3])],
                               [$4=yes],
                               [$4=no])])
@@ -801,16 +804,13 @@ dnl ============================================================================
 dnl Check for ffsl(3), and fail if not found.  This function exists on all
 dnl platforms that jemalloc currently has a chance of functioning on without
 dnl modification.
-JE_COMPILABLE([a program using ffsl],
-              [
-              #include <string.h>
-              ],
-              [
+JE_COMPILABLE([a program using ffsl], [
+#include <string.h>
+], [
 	{
 		int rv = ffsl(0x08);
 	}
-              ],
-              [je_cv_function_ffsl])
+], [je_cv_function_ffsl])
 if test "x${je_cv_function_ffsl}" != "xyes" ; then
    AC_MSG_ERROR([Cannot build without ffsl(3)])
 fi

include/jemalloc/internal/jemalloc_internal.h.in

@@ -566,10 +566,7 @@ sa2u(size_t size, size_t alignment, size_t *run_size_p)
 	}
 }
 
-/*
- * Choose an arena based on a per-thread value (fast-path code, calls slow-path
- * code if necessary).
- */
+/* Choose an arena based on a per-thread value. */
 JEMALLOC_INLINE arena_t *
 choose_arena(void)
 {

src/jemalloc.c

@@ -101,10 +101,7 @@ arenas_extend(unsigned ind)
 	return (arenas[0]);
 }
 
-/*
- * Choose an arena based on a per-thread value (slow-path code only, called
- * only by choose_arena()).
- */
+/* Slow path, called only by choose_arena(). */
 arena_t *
 choose_arena_hard(void)
 {