[asan] Fix asan initialization failure with newer (2.23+) glibc in use.

This patch tries to fix https://llvm.org/bugs/show_bug.cgi?id=27310 by using the same hack for malloc as we use for calloc: allocate corresponding memory from internal buffer when ASan is not initialized.
This way we could avoid nasty '==6987==AddressSanitizer CHECK failed: ../../../../libsanitizer/asan/asan_rtl.cc:556 "((!asan_init_is_running && "ASan init calls itself!")) != (0)" (0x0, 0x0)' errors in
environments with glibc 2.23+ in use, where _dl_signal_error, called from dlsym for undefined symbols calls malloc in order to get a buffer for error message.

Differential Revision: http://reviews.llvm.org/D20235

llvm-svn: 269633