src: introduce upx::max and friends; updates for clang-19 git snapshot

src/p_unix.cpp

@@ -599,8 +599,6 @@ int PackUnix::find_overlay_offset(MemBuffer const &buf)
 // See notes there.
 **************************************************************************/
 
-static unsigned umax(unsigned a, unsigned b) {return (a < b) ? b : a;}
-
 void PackUnix::unpack(OutputFile *fo)
 {
     b_info bhdr;
@@ -671,7 +669,7 @@ void PackUnix::unpack(OutputFile *fo)
         // first flag bits of NRV_d32, the 5-byte info of LZMA, etc.
         // Fuzzers may try sz_cpr shorter than possible.
         // Use some OVERHEAD for safety.
-        i = blocksize + OVERHEAD - umax(12, sz_cpr);
+        i = blocksize + OVERHEAD - upx::umax(12u, sz_cpr);
         if (i < 0)
             throwCantUnpack("corrupt b_info");
         fi->readx(buf+i, sz_cpr);