Fix bug 11736: Minor glslang compilation fixes: Correct "currentChar" logic for recently switched to unsigned size_t locations, and protect more pool guard code with #ifdef.

git-svn-id: https://cvs.khronos.org/svn/repos/ogl/trunk/ecosystem/public/sdk/tools/glslang@25512 e7fa87d3-cd2b-0410-9028-fcbf551c1848

glslang/MachineIndependent/Scan.h

@@ -93,9 +93,11 @@ public:
             do {
                 --currentSource;
             } while (currentSource > 0 && lengths[currentSource] == 0);
-            currentChar = lengths[currentSource] - 1;
-            if (currentChar < 0)
+            if (lengths[currentSource] == 0) {
+                // set to 0 if we've backed up to the start of an empty string
                 currentChar = 0;
+            } else
+                currentChar = lengths[currentSource] - 1;
         }
         if (peek() == '\n')
             --loc[currentSource].line;