Memory pool alignment error when alignment is set to be greater than the default (thanks John Ridges for the report)

[bennylp]

When alignment is set to be greater than default alignment, the memory allocated from the pool may not be aligned to the required alignment, because the pool's start memory block is not aligned to the required alignment.

Note that ticket #980 had attempted to fix this but it missed few other locations where the bug occurs.

[bennylp]

Fixed in r3081:

• fixed the pool allocation routines in PJLIB,
• add alignment test in pjlib-test (only useful if PJ_POOL_ALIGNMENT is configured in config_site.h),
• fixed other pool tests in pjlib-test which are broken when PJ_POOL_ALIGNMENT is enlarged

[bennylp]

In r3082:

• bug in aligning pointer if sizeof(long) is less than sizeof(void*). Thanks John Ridges for pointing this out