Start refactoring of htpasswd and htdbm

- Move many common code parts into separate source file. This adds some
  of htpasswd's recent improvements to htdbm.
- Rework salt generation to use the full 48bit of entropy for MD5
  Previously, it would only generate 2^32 different salts on a given
  platform.
- Use apr_getopt().
Submitted by: sf
Backport of r1395253 from trunk.

Add passwd_common.c build support for Windows and Netware
Submitted by: sf
Backport of r1395254 from trunk.

Add support for bcrypt (requires apr-util 1.5 or higher).
PR: 49288
Submitted by: sf
Backport of r1395255 from trunk.

Optionally read passwords from stdin as more secure alternative to -b.
PR: 40243
Submitted by: Adomas Paltanavicius <adomas paltanavicius gmail com>, sf
Backport of r1395256 from trunk.
Submitted by: Adomas Paltanavicius <adomas paltanavicius gmail com>, sf

Removed __func__ usage which is c99.
Submitted by: sf
Backport of r1395792 from trunk.

All of the above backported by: sf
All of the above reviewed by: sf, gsmith, rjung

fix unresolved external symbol __imp__UuidCreate error
Submitted by: gsmith
Backported by: gsmith
Reviewed by: gsmith, rjung
Backport of r1419084 from trunk.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1420084 13f79535-47bb-0310-9956-ffa450edef68