ldso: Export 'lx_syscall' for base-linux

The syscall library in not linked to dynamic binaries anymore, hence ldso need
to export the required symbols

Follow up to #1017
blk_cache: fix deadlock in allocator hierarchy

This commit generalizes the bit array in 'base/util/bit_array.h',
so that it can be used in a statically, when the array size is known
at compile time, or dynamically. It uses the dynamic approach of the
bit array for a more generalized version of the packet allocator,
formerly only used by NIC session clients. The more generic packet
allocator is used by the block cache to circumvent the allocation
deadlock described in issue #1059.

Fixes #1059
Fixup for "blk_cache: fix deadlock in allocator hierarchy"
block cache: quota to small for foc_x86_64
core: lower default verbosity when quota exceeds

* only print quota exceeded message and statistic when explicitly enabled
* turn init's error message "cannot respond to request" into a warning
another fixup "base: setup thread object for main thread in CRT0"

ref #989

This patch fixes the build problems of noux packages on base-linux.
ldso: don't destruct Rm_area singleton in file.cc

This is needed to avoid access to invalid caps in forked noux programs.

ref #989
base: Fix stack pointer alignment for ARM

After some research we found that the stack pointer on ARM platforms must be
at least double word aligned (See: "Procedure Call Standard for the ARM
Architecture" - 5.2.1.1). Since a 'call' on ARM will not result in a stack pointer
change (like on x86), the current behavior resulted in a 4 Byte aligned stack
only.

Follow up to #1043