DrawText text renderer plugin: Fix OGLFT.cpp compile failure on Debian sid and jessie.

Compile failed in Debian upstream due to changes in header file
locations in FreeType-2. Make detection of the relevant header file
automatic, so code adapts at compile time, like with all other
FreeType-2 header files.

-> Compile tested on OSX, works, should hopefully fix Debian build
failure.
DrawText FTGL text rendering plugin: Make less chatty.

Raise min verbosity levels for info/debug messages to avoid swamping
the console with messages at verbosity 4 and higher.
-> OSX 64-Bit plugin rebuilt and tested. Much better :)
-> Rebuild for Linux pending.
Screen for 64-Bit Octave on OSX rebuilt for testing.