sci-mathematics/giac: Ebuild fix

FLTK paths added to CPPFLAGS and LDFLAGS.
The code invokes fltk-config, which breaks crosscompileability.
sci-mathematics/giac: Ebuild improvement

Added PAX-checks and exception for MPROTECT
sci-mathematics/giac: EAPI bump
sci-mathematics/giac: Ebuild fix

Stupid error in econfargs corrected.
Merge pull request #252 from Doeme/master

sci-mathematics/giac changes