glsl2: Wrap includes of C interfaces with extern "C".
diff --git a/src/glsl/linker.cpp b/src/glsl/linker.cpp
index ba382fe..8547f74 100644
--- a/src/glsl/linker.cpp
+++ b/src/glsl/linker.cpp
@@ -77,7 +77,9 @@
 #include "ir.h"
 #include "ir_optimization.h"
 #include "program.h"
+extern "C" {
 #include "hash_table.h"
+}
 
 /**
  * Visitor that determines whether or not a variable is ever written.