add packages cloog isl and use for gcc optimisations
patch qt: mingw-w64 fix
package gcc: retry mingw-w64 crt build
Merge pull request #262 from tonytheodore/cloog-isl

add packages cloog isl and use for gcc optimisations
packages vo-aacenc vo-amrwbenc: fix update macros
package pkgconf: disable updates
package automake: disable doc build
update package gd
package icu4c: add update macro
packages gcc-*: configure with --disable-shared

Avoids problem with dynamic linking of gcc's configure's conftest
for ISL version discussed at https://github.com/mxe/mxe/pull/262.