Implemented support for GL_LUMINANCE[_ALPHA]

A "Note" was added to from_int_L(), that discusses an issue with going from
intermediate values to "luminance" values.
Merge pull request #67 from IanAtLunarG/pxfmt_140515a

Implemented support for GL_LUMINANCE[_ALPHA]
UI: VertexArrayExplorer now supports client-side element arrays and additional display options
* element count, byte offset, and base vertex can now be adjusted in the UI to better explorer the element and vertex arrays.
* If a draw call is selected, the parameters of the call are now fed into the Explorer to provide a better user interaction.
  * Note that glMultiDraw* functions are not yet supported in this manner; Instanced draws are still not fully supported.
* Improved detection of out-of-bounds cases when accessing the element or vertex arrays
* The order of UI updates is a bit complicated here. Hopefully I can clarify:
  1) The vogleditor updates the explorer with parameters of the current API call (if applicable); UI box are updated
  2) The vogleditor updates the explorer with all the VAOs and sets the current one.
  3) When a VAO is selected, the referenced buffers are collected and the column headers to show the buffers
  4) VertexArrayExplorer UI boxes are updated to reflect either the display options set from the API call, or the element count is adjusted based on the data type selected and the size of the supplied element array.
  5) The vertex array table is populated with data from the buffers, using the currently selected values in the UI
* Changing the element data type will cause the element count to change if the API call has not set display options. It will adjust to avoid indexing beyond the end of the element array. The user may further adjust the UI options, and any invalid indexing will display "Out of bounds" in the appropriate cell of the table.
Merge branch 'master' of https://github.com/ValveSoftware/vogl
Add SDL license note.
Merge branch 'master' of https://github.com/ValveSoftware/vogl
Cleanup warning mesasges on Windows
Merge branch 'master' of https://github.com/ValveSoftware/vogl
Refactor and clean up replay tool.
Merge branch 'master' of https://github.com/ValveSoftware/vogl
Convert erroneous tabs->spaces. Fix linker error on windows introduced by voglreplay refactoring.
Merge pull request #69 from vMcJohn/master

Fix windows warnings - All tests passed on linux. Accepting.
Voglreplay refactor.
Replayer: Benchmark mode now defaults to NOT teardown & restore GL context state.
* Cmd line option: --allow_state_teardown has been added to re-enable the teardown & restore when --benchmark is also used.
* Looping behavior outside of benchmark mode has not been changed
cmake: link vogltest against libGL found during configure
glx: query w/h via glXQueryDrawable + trap errors

When creating a context vogl queries the size of the associated
drawable. This updates it to use glXQueryDrawable instead of
XGetGeometry in case the application is passing a GLXDrawable e.g.
created via glXCreateWindow which may result in a BadDrawable error with
XGetGeometry.

To be extra careful not to leak an X error from our own internal X
requests back to the application, this also adds some utilities for
trapping X errors within vogl.
Check for negative shader src len ⇒ \0 terminated
consider a 3.1 fwd compat ctx as core-profile too

Forward compatibility implies no deprecated apis and since the
deprecation model was introduced for 3.1 it seems to be equivalent to a
core-profile too.
Allow 'redundant' MakeCurrent to update drawable
Use shared wrapper for safely querying glx drawable size