Filter pattern for specifying scopes in which logging is enabled.

A filter is a list of comma-separated terms of the form:

  <pattern>

If <pattern> contains a "*" or "?" character, it is interpreted as a glob pattern.
Otherwise, it is interpreted as a substring. If <pattern> is empty, it
matches every scope. The term ~<pattern> is used to disable logging for specified pattern.
A filter with no terms matches every scope.

Examples of filters:
---------
  (empty string)

  Enables logging for all scopes.
---------
  PointsToAnalysis,CodeGen

  Matches and enables logging for scopes containing "CodeGen" or "PointsToAnalysis".
---------
  CodeGen*

  Matches and enables logging for scopes starting with "CodeGen".
---------
CodeGen, ~PointsToAnalysis

Matches scopes containing "CodeGen" and enables logging for them,
while for scopes containing "PointsToAnalysis" logging is disabled.
