• Fix an initial problem encountered with libgiac: it could not be linked with other libraries.

+ several other fixes and improvments for math/giacxcas:

• do not link cocoalib with the static libgmp (other binaries are linked against the dynamic one)
• fixes Fl::set_fonts for some badly registered fonts
• remove USE_GCC: a runtime has been done and it seems OK
• add USES=localbase to simplify the flags
• add 2 missing libraries (libecm and libmpf): unless explicitely disabled they are used
• Makefiles had been patched to install the in-line docs under $docdir => make programs and files coherent with that
• add a TEST_TARGET: all tests but 2 pass
• add USE_PERL5=run, because pgiac is a Perl script.

PR: 246049
Submitted by: /me
Approved by: yuri@ (maintainer)