[cling] Unroll the pointer-check cache loop.

interpreter/cling/lib/Utils/PlatformPosix.cpp

@@ -70,8 +70,9 @@ namespace {
     bool operator () (const void* P) {
       if (FD == -1)
         return false;
-
-      if (std::find(lines.begin(), lines.end(), P) != lines.end())
+      // std::find is considerably slower, do manual search instead.
+      if (P == lines[0] || P == lines[1] || P == lines[2] || P == lines[3]
+          || P == lines[4] || P == lines[5] || P == lines[6] || P == lines[7])
         return true;
 
       // There is a POSIX way of finding whether an address