Patches for OSTYPE=linux-gnu

[Jan Prikryl <prikryl@xxxxxxxx>]

Hi,

attached are four patches to different makefiles and makefile includes
improving Linux support. Summary:

(1) takes care of OSTYPE being reported as "linux-gnu" (Redhat-6.2 at
    least) 
(2) in a dirty way fixes the double vs. float problems (via
    -D_POSIX_SOURCE -D_XOPEN_SOURCE)

-- jan

--------------------+------------------------------------------------------
 Jan Prikryl        | vr|vis center for virtual reality and visualisation
 <prikryl@xxxxxxxx> | http://www.vrvis.at
--------------------+------------------------------------------------------

patch1
Description: Text document

patch2
Description: Text document

patch3
Description: Text document

patch4
Description: Text document