Support nasm USE32 and GLOBAL directives.

Make directives case-insensitive.

Both nasm and gnu assembler use case insensitive directives.

Added tests for intel/nasm label artithmetic

x86: support salc,int1, fsetpm instructions. also added testcase suite/regress/x86_special_insn.py. see issue #58

Fix memory leaks.

Add regress test for call label on X86

Uses new / delete like in mrexodia's patch, deletes things allocated
in ks_asm properly, clean up properly in ks_close. Removed 2 deletes
from the MCObjectStreamer destructor that we re-use in a second run
of ks_asm on the same keystone instance.

Valgrind shows no invalid reads and no memory leaks in keystone after
running the regression tests.

Don't store StringRef to StringRef::lower().

lower() returns a new string which should be stored and not just
referenced. Valgrind shows invalid reads if you just store the ref.

revert to use calloc/free rather than new/delete for ks_struct. this fixes a segfault on Ubuntu 14.04 64bit