This makes sure that labels for data symbols directly after
functions get properly 4-byte-aligned (when the source is assembled
in thumb mode).

Previously, if declaring a data symbol directly after a function, the
symbol could end up pointing to the unaligned address (if the total
size of the thumb function didn't end up being a multiple of 4). The
data in the symbol itself ended up aligned, but the symbol pointed to
the preceding unaligned position.

That is, a source file looking like this:
---
   ...
   ENDP

symbol
   DCD 0x12345678
---

could end up being assembled into
symbol:
  xxxxx2: 0000
  xxxxx4: 5678
  xxxxx6: 1234

(This doesn't happen if the symbol label is on the same line as the
DCD directive.)

By adding an ALIGN 4 directly after the ENDP we make sure the symbol
itself gets aligned properly.

This isn't an issue with the original, untranslated arm source,
since it only is built in arm mode where all instructions are 4 byte,
and since the gnu assembler automatically adds the padding before the
symbol even in thumb mode.

Change-Id: Iadbeebd656b0197e423e79a12a7d3ef8859cf445