Fixes "deprecated conversion from string constant to 'char*'" compiler warning.

diff --git a/src/os/linux/vm/jvm_linux.cpp b/src/os/linux/vm/jvm_linux.cpp
--- a/src/os/linux/vm/jvm_linux.cpp
+++ b/src/os/linux/vm/jvm_linux.cpp
@@ -132,7 +132,7 @@
 */
 
 struct siglabel {
-  char *name;
+  const char *name;
   int   number;
 };
 
diff --git a/src/os/linux/vm/os_linux.cpp b/src/os/linux/vm/os_linux.cpp
--- a/src/os/linux/vm/os_linux.cpp
+++ b/src/os/linux/vm/os_linux.cpp
@@ -213,7 +213,7 @@
 // the system call returns 1.  This causes the VM to act as if it is
 // a single processor and elide locking (see is_MP() call).
 static bool unsafe_chroot_detected = false;
-static char *unstable_chroot_error = "/proc file system not found.\n"
+static const char *unstable_chroot_error = "/proc file system not found.\n"
               "Java may be unstable running multithreaded in a chroot "
               "environment on Linux when /proc filesystem is not mounted.";
 
@@ -557,13 +557,13 @@
         // NPTL:
         if (sysconf(_SC_THREAD_THREADS_MAX) > 0) {
            free(str);
-           str = "linuxthreads";
+           str = (char *) "linuxthreads";
         }
      }
      os::Linux::set_libpthread_version(str);
   } else {
      // glibc before 2.3.2 only has LinuxThreads.
-     os::Linux::set_libpthread_version("linuxthreads");
+     os::Linux::set_libpthread_version((char *) "linuxthreads");
   }
 
   if (strstr(libpthread_version(), "NPTL")) {
@@ -4538,7 +4538,7 @@
 // Unlike system(), this function can be called from signal handler. It
 // doesn't block SIGINT et al.
 int os::fork_and_exec(char* cmd) {
-  char * argv[4];
+  const char * argv[4];
   argv[0] = "sh";
   argv[1] = "-c";
   argv[2] = cmd;