[PATCH] Fix warnings (and incorrect code?) for gcc-4.2.0

In gcc-4.2.0's release notes:

  A new command line option -Waddress has been added to warn about
  suspicious uses of memory addresses as, for example, using the
  address of a function in a conditional expression, and comparisons
  against the memory address of a string literal. This warning is
  enabled by -Wall.

This finds three lines in ares_init.c that look like they contain
mistakes. There's a character array that contains a string or just a
'\0', and it looks like the three tests involved are supposed to be
checking if ipbufpfx[0] == '\0' or not, but they are instead testing
the address of ipbufpfx.

The attached patch attempts to fix this. Is that what's intended?
        

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Brad Spencer - spencer@jacknife.org - http://jacknife.org/