Implemented developer-configurable malloc()/free().

Details:
- Replaced all instances of bli_malloc() and bli_free() with one of:
  - bli_malloc_pool()/bli_free_pool()
  - bli_malloc_user()/bli_free_user()
  - bli_malloc_intl()/bli_free_intl()
  each of which can be configured to call malloc()/free() substitutes,
  so long as the substitute functions have the same function type
  signatures as malloc() and free() defined by C's stdlib.h. The _pool()
  function is called when allocating blocks for the memory pools (used
  for packing buffers, primarily), the _user() function is called when
  obj_t's are created (via bli_obj_create() and friends), and the _intl()
  function is called for internal use by BLIS, such as when creating
  control tree nodes or temporary buffers for manipulating internal data
  structures. Substitutes for any of the three types of bli_malloc() may
  be specified by #defining the following pairs of cpp macros in
  bli_kernel.h:
  - BLIS_MALLOC_POOL/BLIS_FREE_POOL
  - BLIS_MALLOC_USER/BLIS_FREE_USER
  - BLIS_MALLOC_INTL/BLIS_FREE_INTL
  to be the name of the substitute functions. (Obviously, the object
  code that contains these functions must be provided at link-time.)
  These macros default to malloc() and free(). Subsitute functions are
  also automatically prototyped by BLIS (in bli_malloc_prototypes.h).
- Removed definitions for bli_malloc() and bli_free().
- Note that bli_malloc_pool() and bli_malloc_user() are now defined in
  terms of a new function, bli_malloc_align(), which aligns memory to an
  arbitrary (power of two) alignment boundary, but does so manually,
  whereas before alignment was performed behind the scenes by
  posix_memalign(). Currently, bli_malloc_intl() is defined in terms
  of bli_malloc_noalign(), which serves as a simple wrapper to the
  designated function that is passed in (e.g. BLIS_MALLOC_INTL).
  Similarly, there are bli_free_align() and bli_free_noalign(), which
  are used in concert with their bli_malloc_*() counterparts.

frame/include/bli_kernel_macro_defs.h

@@ -38,8 +38,49 @@
 
 // -- MEMORY ALLOCATION --------------------------------------------------------
 
-// Size of a virtual memory page. This is used to align certain memory
-// buffers which are allocated and used internally.
+// Memory allocation functions. These macros define the three types of
+// malloc()-style functions, and their free() counterparts: one for each
+// type of memory to be allocated.
+// NOTE: ANY ALTERNATIVE TO malloc()/free() USED FOR ANY OF THE FOLLOWING
+// THREE PAIRS OF MACROS MUST USE THE SAME FUNCTION PROTOTYPE AS malloc()
+// and free():
+//
+//   void* malloc( size_t size );
+//   void  free( void* p );
+//
+
+// This allocation function is called to allocate memory for blocks within
+// BLIS's internal memory pools.
+#ifndef BLIS_MALLOC_POOL
+#define BLIS_MALLOC_POOL                 malloc
+#endif
+
+#ifndef BLIS_FREE_POOL
+#define BLIS_FREE_POOL                   free
+#endif
+
+// This allocation function is called to allocate memory for internally-
+// used objects and structures, such as control tree nodes.
+#ifndef BLIS_MALLOC_INTL
+#define BLIS_MALLOC_INTL                 malloc
+#endif
+
+#ifndef BLIS_FREE_INTL
+#define BLIS_FREE_INTL                   free
+#endif
+
+// This allocation function is called to allocate memory for objects
+// created by user-level API functions, such as bli_obj_create().
+#ifndef BLIS_MALLOC_USER
+#define BLIS_MALLOC_USER                 malloc
+#endif
+
+#ifndef BLIS_FREE_USER
+#define BLIS_FREE_USER                   free
+#endif
+
+// Size of a virtual memory page. This is used to align blocks within the
+// memory pools.
 #ifndef BLIS_PAGE_SIZE
 #define BLIS_PAGE_SIZE                   4096
 #endif
@@ -76,17 +117,16 @@
 // functions.
 #define BLIS_STACK_BUF_ALIGN_SIZE        BLIS_SIMD_ALIGN_SIZE
 
-// Alignment size used when allocating memory dynamically from the operating
-// system (eg: posix_memalign()). To disable heap alignment and just use
-// malloc() instead, set this to 1.
+// Alignment size used when allocating memory via BLIS_MALLOC_USER.
+// To disable heap alignment, set this to 1.
 #define BLIS_HEAP_ADDR_ALIGN_SIZE        BLIS_SIMD_ALIGN_SIZE
 
-// Alignment size used when sizing leading dimensions of dynamically
-// allocated memory.
+// Alignment size used when sizing leading dimensions of memory allocated
+// via BLIS_MALLOC_USER.
 #define BLIS_HEAP_STRIDE_ALIGN_SIZE      BLIS_SIMD_ALIGN_SIZE
 
 // Alignment size used when allocating blocks to the internal memory
-// pool (for packing buffers).
+// pool, via BLIS_MALLOC_POOL.
 #define BLIS_POOL_ADDR_ALIGN_SIZE        BLIS_PAGE_SIZE