libphoenix: strftime() multiple (2) issues

[niewim19]

Issue 1: Not supported specifiers in FORMAT string:

Following specifiers are not supported:
%C, %D, %F, %g, %G, %h, %I, %p, %r, %R, %t, %T, %u, %U, %V, %W, %x, %X, %z

Issue 2: optional specifiers parameters not supported in FORMAT string:

All additional specifier flags are not supported:

• 0
• +,
• minimum field width,
• E or 0 modifier