make depend with solaris c compiler (ITS#595)

[helm@fionn.es.net]

Full_Name: michael helm
Version: 1.2.x
OS: solaris
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (24.4.254.120)


Didn't see this in the faq/problem report list.

make depend runs the c compiler with options that sun workshop c (4.2 or 5)
doesn't understand. 

Setenv CC_MKDEP_FLAGS -xM1 
will cause mkdep to do something reasonable.
This should be tested for & set up by autoconf but it's not
immediately obvious how to wedge that change in.