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

Don't output the symbol's name instead of its value.

Besides fixing `ldr Rd,=label` on ARM, this also fixes defining addresses
of symbols as literals (`.int label1`) on all platforms.

ignore all directories with the build prefix

Add ks_asm() Address to symbol offset.

Add test for ldr Rd, =label on ARM.

Currently, =label is interpreted as a string instead of a symbol.

By adding BaseAddress to MCContext, passing it from ks_asm and using it
to initialise the address of the first fragment we make sure that
symbols get the right absolute offset.

This checks whether the addr passed to ks.asm() is used.