(ITS#5215) Use of ln is hardcoded in some files

Full_Name: Emmanuel Duru Version: 2.3.38 OS: Windows URL: ftp://ftp.openldap.org/incoming/ Submission from: (NULL) (195.68.44.148)

configure allows the use of "cp" instead of "ln", but the build/shtool tool uses a hardcoded "ln" (line 1266). Some makefiles (libraries/liblunicode, libraries/libldap_r and servers/slapd/back-hdb) use a hardcoded "-s" option. This is a problem on Windows because in cygwin environment "cp -s" behaves the same way as "ln -s". The use of "ln" is not welcome here because it creates a Windows shortcut, which is not understood by mingw compiler.