[NFR] kernel/memory.c optimizations

[ghost]

• do not call erealloc() on every call to phalcon_memory_observe()/phalcon_memory_alloc()
• do not waste the very first memory frame
• free the root memory frame and its structures only during RSHUTDOWN or MSHUTDOWN; this helps reduce the number of calls to emalloc()/efree()
• use ecalloc() instead of emalloc() when allocating a memory frame (no need to zero out memory)
• safe erealloc()
• number of observed variables per frame is not limited with PHALCON_MAX_MEMORY_STACK anymore

On a large scale, when running manual-unit.php, there are almost 15,000 less calls to efree(), 68,000 less calls to emalloc(), cost of the call to phalcon_memory_observe() is almost 2 times less now (tested with callgrind).

[ghost]

Rebased against the current HEAD

[phalcon]

This is great!!

[phalcon]

@niden and @sjinks, can you take a look at this please? https://bugzilla.redhat.com/show_bug.cgi?id=977208#c23

[ghost]

Regarding the CPU detection: this is how I did that for Ubuntu/Debian: https://github.com/phalcon/php-phalcon/blob/raring/debian/rules

PHALCON_DIR = cphalcon/build/safe
DEB_HOST_ARCH ?= $(shell dpkg-architecture -qDEB_HOST_ARCH)

ifeq ($(DEB_HOST_ARCH),$(filter $(DEB_HOST_ARCH),i386))
PHALCON_DIR = cphalcon/build/32bits
endif

ifeq ($(DEB_HOST_ARCH),$(filter $(DEB_HOST_ARCH),amd64))
PHALCON_DIR = cphalcon/build/64bits
endif

They can't use -march=native on the build host anyway so they don't need to run gccarch anyway.

[ghost]

Database, memcached etc tests that depend on external services: in 1.2.1 we have implemented a way to skip the test if the service is not available.

Probably we should release 1.2.1 soon so that they don't hack the unit tests much :-)