POSIX compatibility change for including wait.h in UNIXProcess_md.c

[Jonathan Lu]

Hi core-libs-dev,

It was found that solaris/native/java/lang/UNIXProcess_md.c includes 
<wait.h> which does not seem to be compliant with POSIX specification, 
in which the expected header file name should be <sys/wait.h>. see 
http://en.wikipedia.org/wiki/C_POSIX_library. I also performed a 'grep' 
for the code base, it seems nowhere else needs to be changed so far.

So here is a simple patch to adjust this issue, any suggestions?
http://cr.openjdk.java.net/~luchsh/wait_h_POSIX_comp/

Cheers
- Jonathan