Fix OpLine prepending OpFunction reports wrong file when #line is present

Test/spv.pp.line.frag

@@ -1,4 +1,5 @@
 #version 140
+#extension GL_GOOGLE_cpp_style_line_directive : require
 
 uniform sampler1D       texSampler1D;
 uniform sampler2D       texSampler2D;
@@ -8,9 +9,20 @@ varying vec4 u;
 
 in  vec2 coords2D;
 
+#line 0 "header.h"
+float myAbs(float x) {
+    if (x > 0) {
+        return x;
+    }
+    else {
+        return -x;
+    }
+}
+
+#line 22 "spv.pp.line.frag"
 void main()
 {
-    float blendscale = 1.789;
+    float blendscale = myAbs(1.789);
     float bias       = 2.0;
     float coords1D   = 1.789;
     vec4  color      = vec4(0.0, 0.0, 0.0, 0.0);