[gui] max-width compute result are incorrect

[lc-soft]

Expected result:

Actual result:

[lc-soft]

Here has a stylesheet selection bug from src/gui/css_library.c#L1104

Example:

.col-6 {
  display: inline-block;
  max-width: 100%;
}
 .col {
  width: 100%;
  max-width: 100%;
}
.col-6 {
  max-width: 50%;
}

The effect of the above code is equivalent to the following code:

.col-6 {
  display: inline-block;
  max-width: 50%;
}
 .col {
  width: 100%;
  max-width: 100%;
}

The two stylesheets will be merged into a single styleesheet.

[lc-soft]

Done.