travis: add nearly all gallium drivers to the list
travis: add nearly all gallium drivers to the list

Note: we need the explicit --enable-freedreno for libdrm since the
latter is 'smart' and disables it if building on !arm platforms.

The radeonsi and swr are explicitly left out since they require
'too-recent' LLVM - 3.6

Signed-off-by: Emil Velikov <f20878473f414da183da19ee25c8722cc1d711e4@collabora.com>
Reviewed-by: Andres Gomez <1948e91ee7852f22bc880d172a32ffca98fb60fa@igalia.com>
Reviewed-by: Eric Anholt <96f164ad4d9b2b0dacf8ebee2bb1eeb3aa69adf1@anholt.net>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler