Screen: Reenable text rendering for OpenGL-ES1.x, cleanups.

Unconditionally enable text rendering via drawtext plugin on
OES rendering api. Use a different plugin for text rendering
on OpenGL-ES: libptbdrawtext_ftglesXXX. XXX is nothing or 64
for 32-Bit resp. 64-Bit intel processors, arm or arm64 on
32-Bit resp. 64-Bit ARM processors. The probe sequence also
always tries the generic libptbdrawtext... generic names to
take the different software packaging on NeuroDebian/Debian/Ubuntu
into account.

Cleanup some startup messages - shorten them.

Also change license for all drawtext plugins from LGPLv2+ to
MIT for better consistency with the distro as a whole.

Screen for 64-Bit Octave on Linux rebuilt and tested.
Add support for text rendering on Linux with OpenGL-ES1.1 rendering api.

The new plugin libptbdrawtext_ftgles.cpp implements a new text renderer
which is based on FTGLES, the "FreeType for OpenGL Embedded Subset"
library. The library is statically built and linked against our code
for simplicity of installation. The library is released under a MIT
style license, just as our plugin.

libftgles_intel64.a is a statically built FTGLES binary for 64-Bit Intel
cpus. The subfolder FTGL/ contains the header and class definitions
needed to compile and link our plugin aginst FTGLES. We need to use
a slightly patched implementation to make it Linux ready, as the current
upstream supports only Android and iOS build platforms. However, tweaks
are minor and will be upstreamed asap.

Psychtoolbox/PsychBasic/PsychPlugins/libptbdrawtext_ftgles64.so.1
is the new text rendering plugin which will get loaded by Screen()
on 64-Bit Intel platforms if OpenGL-ES1.1 is active as rendering
backend.

The renderer uses texture mapping / blitting for glyph rendering
and stores glyph images as subregions in a texture atlas to minimize
memory consumption and optimize performance on embedded hardware.

It support unicode rendering, anti-aliasing via alpha blending,
bounding box computation and layouting, choose of foreground and
background color, text size, style and font. Identical to the
desktop implementation.

Current limitations as imposed by the current FTGLES implementation:

- Text alpha-blending and text anti-aliasing can't be disabled,
  text is therefore always rendered with anti-aliasing. This is
  only a concern for rendering to color index overlays, e.g., for
  driving Bits+, Bits#, Data/View/ProPixx hardware, but embedded
  devices are not really expected to drive such hardware anyway.

- Text index in a multi-index font definition file can't be selected,
  which may impair selection of text style for some font files, although
  no such impairment was observed in our demos.

- Mirrored drawing of text as in DrawMirroredTextDemo.m does not work,
  as geometric transformations are done differently during texture
  blitting.

Other than that, stuff looks pretty good when testing on X11/EGL on
the Laptop. Tests on Nexus-7 pending.