[build] reorder SUBDIRS to only recurse once

Currently, both GLX and GLdispatch recurse into src/util/trace.  This causes
problems for parallel make, and breaks distclean because the first recursion
into src/util/trace deletes the Makefile, causing the second recursion to fail.

Instead, recurse directly into util from src/Makefile.am, putting it ahead of
both GLX and GLdispatch in SUBDIRS.  This means that you can't just go into
src/GLX and type make, but it fixes parallel builds and distclean.

Signed-off-by: Aaron Plattner <aplattner@nvidia.com>
[build] fix srcdir != builddir mistakes

When configure is run from a directory other than the source directory, various
files fail to compile because the include paths use $(builddir) or
$(top_builddir) when the source is actually in $(srcdir) or $(top_srcdir).

Signed-off-by: Aaron Plattner <aplattner@nvidia.com>
[build] enable silent rules by default

Automake still defaults to verbose output unless you explicitly request that the
silent rules be enabled by default.  It's possible to only enable the silent
rules on versions of automake that actually support it, but automake 1.11 has
been around for long enough that it seems easier to just bump the minimum
required version.

Add the boilerplate required to turn on the silent rules by default.  They can
still be disabled by passing --disable-silent-rules to configure or by passing
V=0 on the make command line.

Signed-off-by: Aaron Plattner <aplattner@nvidia.com>