Fix small memory leak in expression parser.

Thanks to the valgrind.
Merge branch 'fix-mem-leak-in-eval-expression'

Fix memory leak on evaluation expressions.  Temporary variable was not
freed.
Better order of command-line command checks

Check for exclamation and question marks before checking number of
arguments.
Ignore NULL arrays in free_string_array()
Show better unmatched quotes errors for commands
Merge branch 'small-command-parser-enhancements'

Fix several issues with command parser.  Not a real problems, but
annoyed a bit.
Fix typedef redefinition in search.h

Thanks to Daniel R. (a.k.a. reicheltd).
Merge branch 'fix-fileview-typedef-redefinition'

Fix typedef redefinition.  Turns out that typedef should be defined
exactly the same way multiple times.