Fix prpgrep not searching some objects properly

For example, `prpgrep plSoundBuffer BahroCave_District_YeeshaCave.prp`
found no results, even though that page contains many plSoundBuffer
objects (and other objects that reference them).

Not sure what exactly was wrong with the custom GetLine function here,
but replacing it with the standard hsStream::readLine fixes it.

Tools/src/prpgrep.cpp

@@ -22,46 +22,12 @@
 #include <string_theory/stdio>
 #include <list>
 
-static char lnbuf[4096];
-static char* lnbuf_ptr = &lnbuf[4096];
-
-static ST::string GetLine(hsStream* S)
-{
-    if (lnbuf_ptr >= &lnbuf[4096]) {
-        size_t len = S->size() - S->pos();
-        if (len > 4096)
-            len = 4096;
-        S->read(len, lnbuf);
-        if (len < 4096)
-            lnbuf[len] = 0;
-        lnbuf_ptr = lnbuf;
-    }
-
-    char* bp = lnbuf_ptr;
-    while (true) {
-        if (bp >= &lnbuf[4096]) {
-            ST::string prefix(lnbuf_ptr, bp - lnbuf_ptr);
-            lnbuf_ptr = &lnbuf[4096];
-            return prefix + GetLine(S);
-        } else if (*bp == '\n' || *bp == 0) {
-            ST::string ln(lnbuf_ptr, bp - lnbuf_ptr);
-            lnbuf_ptr = bp + 1;
-            return ln;
-        }
-        bp++;
-    }
-
-    // Should never get here...
-    return ST::string();
-}
-
 static void DoSearch(hsStream* S, const ST::string& pattern,
                      const ST::string& filename, const plKey& key)
 {
     unsigned int ln = 1;
-    lnbuf_ptr = &lnbuf[4096];
     while (!S->eof()) {
-        ST::string text = GetLine(S);
+        ST::string text = S->readLine();
         if (text.find(pattern) >= 0) {
             // Strip initial whitespace
             const char* txtout = text.c_str();