scons: Add option to enable floating-point textures.

Signed-off-by: Vinson Lee <vlee@freedesktop.org>
Reviewed-by: José Fonseca <jfonseca@vmware.com>
diff --git a/common.py b/common.py
index 6121a41..6ff9608 100644
--- a/common.py
+++ b/common.py
@@ -98,5 +98,6 @@
 	opts.Add(BoolOption('debug', 'DEPRECATED: debug build', 'yes'))
 	opts.Add(BoolOption('profile', 'DEPRECATED: profile build', 'no'))
 	opts.Add(BoolOption('quiet', 'DEPRECATED: profile build', 'yes'))
+	opts.Add(BoolOption('texture_float', 'enable floating-point textures and renderbuffers', 'no'))
 	if host_platform == 'windows':
 		opts.Add(EnumOption('MSVS_VERSION', 'MS Visual C++ version', None, allowed_values=('7.1', '8.0', '9.0')))