fix compile errors with gcc 4.1.x and 4.2.x

fix compile errors with gcc 4.1.x and 4.2.x

 - tested with gcc 4.1.2, 4.2.1, 4.4.6, 4.6.3 and 4.7.2
 - disable gcc ignore pragma for "-Warray-bounds" if gcc version < 4.3
   - when I took out the pragma tvheadend compiled fine in all the above compilers, but I assume some version of gcc is issuing a false-positive.
   - "-Warray-bounds" was added in gcc 4.3: http://gcc.gnu.org/gcc-4.3/changes.html
 - fixes typo in cmdline help for -C
 - clarify usage of -a in help description