[TASK] Make system call to php binary reliable, especially on Windows
This solves execution of php binary on windows environments with paths
containing whitespace and special characters (like round brackets). On
windows, commands containing white spaces must be quoted, but quoted
paths may not be escaped, which escapeshellcmd() wrongly does.
This is solved by using escapeshellarg() on windows instead and also
adds more verbose exception messages in the case of failure.
Releases: 1.1, 1.2