fixed -Wreorder warning in HeapProfileTable constructor
fixed gcc warning

We've recently changed old_signal_handler to by integer, so comparing
it with NULL is not good idea.
assert key size in way that is clearer to gcc

Both new and old asserts are checking same condition, however new
assert helps gcc see that out of bounds access is not possible in
root_ array.
assert that ClassSize(0) is 0 instead >=0

Because it's return value being size_t cannot be negative
anyways. This fixes clang warning
use AC_PROG_LIBTOOL to summon libtool

So that older autotools of rhel 5 can be used
actually check result of CheckAddressBits

Previously call to CheckAddressBits was made but nothing was done to
it's result.

I've also make sure that actual size is used in checks and in bumping
up of TCMalloc_SystemTaken.