command line option '/INIFILE' added. Refs: #94.
Partly as proposed in CPC 1.7 rc6.
Fixes a trivial bug in ReadRegistry: len is given in byte and must be multiplied by 2.
Differences to the CPC 1.7 version are:
1. The INI-file name is given as an explicit parameter following the /INIFILE option.
2. The top level section in the INI-file is named after the application.
3. HostMenus.ReadCommandLine is extended with the new option.

Signed-off-by: Josef Templ <josef.templ@gmail.com>