glslang preprocessing: Add -E option to print out preprocessed GLSL, and do the work needed to generate a preprocessed stream. From Andrew Woloszyn <awoloszyn@google.com>.

git-svn-id: https://cvs.khronos.org/svn/repos/ogl/trunk/ecosystem/public/sdk/tools/glslang@31508 e7fa87d3-cd2b-0410-9028-fcbf551c1848

Test/preprocessor.line.vert

@@ -0,0 +1,39 @@
+#line 300
+
+#line 2
+
+
+
+
+
+#line __LINE__ + 3
+
+
+#line __FILE__ + 2
+
+#line __FILE__ * __LINE__
+
+
+#define X 4
+
+#line X
+
+#undef X
+
+#define X(y) y + 3 + 2
+
+#line X(3)
+
+void main() {
+  gl_Position = vec4(__LINE__);
+}
+
+#line X(3) 4
+
+#define Z(y, q) \
+  y*q*2 q
+
+#line Z(2, 3)
+
+#line 1
+