[GRASS5] GMATHLIB support improved

[Markus Neteler]

Hi developers,

I have cleaned up the spreaded numerical functions and moved
them all into GMATHLIB (src/libes/gmath).

Following modules are affected:

 * r.surf.fractal
 * r.surf.gauss
 * r.surf.random
 * i.cca
 * i.pca
 * i.zc
 * i.fft
 * i.shape (src.contrib/CERL/imagery/)

I have tested compilation on Linux, Solaris/SUN and CRAY. Please
report any functionality problems which may occur from (not)
externally declared variables.

Perhaps someone could clean the 

src/libes/gmath/local_proto.h   and
src/libes/gmath/numerical.h

(I am not too familiar with those declaration style).

Cheers

 Markus