gbm: work around mesa linkage issue
gbm: work around mesa linkage issue

Mesa drivers such as i965_dri.so use symbols from libglapi but do not
pull in libglapi (https://bugs.freedesktop.org/show_bug.cgi?id=57702)
so dlopen libglapi before we need it.

Fixes #21: https://github.com/waffle-gl/waffle/pull/21
Reviewed-by: Chad Versace <a557f7f75bf28dc19ac99107f5cc7cd6b3fbdb1a@linux.intel.com>

chadversary/waffle,waffle-gl/waffle,fjhenigman/waffle,chadversary/waffle,evelikov/waffle,chadversary/waffle,maurossi/waffle,dcbaker/waffle,dcbaker/waffle,evelikov/waffle,waffle-gl/waffle,maurossi/waffle,dcbaker/waffle,maurossi/waffle,evelikov/waffle,fjhenigman/waffle,waffle-gl/waffle,waffle-gl/waffle,fjhenigman/waffle