Get rid of warnings

Fix new 'unused variable' warnings in authreg_pgsql.c

Get rid of all 'pointer targets in assignment differ in signedness' warnings:
- All string data are stored referenced as '[const] char *' but never as '[const] unsigned char *'
- Binary data are stored as 'unsigned char *' but never as 'char *'
- Some explicit type cast added for external lib's calls (zlib, OpenSSL and sqlite3)
Merge pull request #15 from eagafonov/master

Get rid of warnings, part 2
Use groupattr value as is if no groupattr_regex defined. Closes #16
README update
ldapfull: Check for ldap group membership on login

Administrators can now supply a <group_dn> configuration directive. If
it is given, only users who are members of this group will be allowed to login

Signed-off-by: Tomasz Sterna <smoku@dcclabs.tv>
Grammear, spelling and other fixes for clarity.
Fixed out-conn-reuse s2s.xml option naming