MEM_HEAP_CREATE_BLOCK() 

PROBLEM
-------

If we give start mysqld with the option --innodb_log_buffer_size=50GB
,then  mem_area_alloc() function fails to allocate memory and returns
NULL.In debug version we assert at this point,but there is no check in
release version and we get a segmentation fault.

FIX
---
Added a log message saying that we are unable to allocate memory.
After this message we assert.

[Approved by Kevin http://rb.no.oracle.com/rb/r/2065 ]