Add a reference Valgrind suppresion file

When using Valgrind for debugging memory leaks and access violations, we
often see a lot of false positives, specially when dealing with OpenGL
that does it own buffer management. This file is an attempt to filter
these false positives.

Note that we are only filtering for the open source Radeon driver and
the list will probably grow to accommodate other setups.

To use the Valgrind with the suppression file for hunting memory leaks,
try something like:

valgrind --leak-check=full --track-origins=yes --suppressions=[path/to/valgrind.sup] ./mapbox-gl

scripts/valgrind.sup

@@ -0,0 +1,91 @@
+{
+   Valgrind gets confused with buffers managed by the graphics driver
+   Memcheck:Leak
+   ...
+   obj:/usr/*/dri/r600_dri.so
+   ...
+}
+{
+   GLFW _glfwCreateCursor()
+   Memcheck:Leak
+   match-leak-kinds: reachable
+   ...
+   obj:/usr/*/libX11.so.6.3.0
+   ...
+   fun:_glfwCreateCursor
+   ...
+}
+{
+   GLFW _glfwPlatform*()
+   Memcheck:Leak
+   match-leak-kinds: reachable
+   ...
+   fun:_glfwPlatform*
+   ...
+}
+{
+   Buffer managed by OpenGL?
+   Memcheck:Cond
+   ...
+   fun:_ZN4mbgl*Uniform*
+   ...
+   fun:_ZN8GLFWView10invalidateEv
+   ...
+}
+{
+   Buffer managed by OpenGL?
+   Memcheck:Cond
+   fun:_ZNSt7__equalILb0EE5equalIPKfS3_EEbT_S4_T0_
+   ...
+   fun:_ZN4mbgl7Painter11renderLayerERKNS_10StyleLayerEPKNS_4Tile2IDEPKSt5arrayIfLm16EE
+}
+{
+   Valgrind doesn't like our make_unique (C++14 polyfill)
+   Memcheck:Leak
+   match-leak-kinds: reachable
+   fun:malloc
+   ...
+   fun:_ZN4mbgl4util11make_unique*
+   ...
+}
+{
+   dlopen doing its magic
+   Memcheck:Leak
+   match-leak-kinds: reachable
+   ...
+   fun:_dl_open
+   ...
+}
+{
+   X11 false positive
+   Memcheck:Leak
+   match-leak-kinds: reachable
+   ...
+   obj:/usr/*/libX11.so.6.3.0
+   ...
+   fun:_XrmInitParseInfo
+   ...
+}
+{
+   OpenSSL false positive
+   Memcheck:Leak
+   ...
+   fun:CRYPTO_malloc
+   ...
+}
+{
+   OpenSSL false positive
+   Memcheck:Leak
+   ...
+   fun:CRYPTO_realloc
+   ...
+}
+{
+   Libcurl false positive
+   Memcheck:Leak
+   fun:malloc
+   ...
+   obj:/usr/*/libcurl.so.4.3.0
+   fun:curl_multi_socket_action
+   ...
+}