Added test cases for ZEND_SIGNED_MULTIPLY_LONG()

Before making changes to the implementation of
ZEND_SIGNED_MULTIPLY_LONG(), add some test cases
to make sure the various implementations remain
equivalent.
Added ARM accelerated implementations for ZEND_SIGNED_MULTIPLY_LONG()

Added inline assembler implementations:
- for 32-bit ARM, as the existing C implementation uses 64-bit
integer arithmetic, which relies on software emulation by libgcc;
- for 64-bit ARM, as the existing C implementation uses long doubles
to check for overflow before using the integer result.

Also updated my email address and fixed some whitespace
Merge branch 'feature/linaro-arm-performance'

* feature/linaro-arm-performance:
  Added ARM accelerated implementations for ZEND_SIGNED_MULTIPLY_LONG()
  Added test cases for ZEND_SIGNED_MULTIPLY_LONG()