[PATCH] Support for microMIPS relocations 1/3

[Rafael Espíndola]

> You should be able to move forward in the assembler. Please ping the
> patch you need reviewed .

Reading the code that was already on trunk I know understand Jack's comment:

> This is testing the direct object emitter which shares some code with llvm-mc, but is a different tool and has different paths.

There indeed was two code paths. That should *not* be the case. The
design of MC is such that the object file produce by llc is just
another representation of the assembly file.  One should never have
code that looks like

if (producing assembly)
   ...
else
  ....

Unless we are truly handling asm only features (comments really).

I have replaced these hacks with smaller ones in r192035. Since I
don't know mips assembly, the directives I added to the asm files are
hacks. I am sure the GNU assembler has proper ones, since gcc has no
direct object emission. Please check which directives and/or command
line options gas uses and replace the hack ones with those.

For any new feature:

* Be sure to implement assembly support.
* Never add a check to hasRawTextSupport or another equivalent check
see if we are doing direct object emission.

Cheers,
Rafael