* Capitalize the function names to fit the style guide.
* Use explicit sizes in the function names to avoid any confusion about
  input or output sizes.
* Use explicit sized types in the functions to avoid potential issues on
  new platforms since a lot of bit-twiddling is used.
* Use size_t for all sizes.
* Use uint8_t for all binary data for input and output data so that pointer
  arithmetic is much easier.
* Move templated function definitions into an .inl file so that
  loadimage.h looks as clean as possible.

BUG=angle:665

Change-Id: Id7173ed66d9e1b7ee3261eea11e77d838cbd2951
Reviewed-on: https://chromium-review.googlesource.com/202590Reviewed-by: Brandon Jones <bajones@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>