[c-index-test] For the '-remap-file=' option use ':' instead of ';' for separator.

lldb does not like semicolon as part of an option.
[c-index-test] Enhance perform_test_reparse_source() to allow remapping a file
at a particular reparsing iteration.

Passing '-remap-file-1=from:to' will remap the files in the second iteration.
[libclang] Record ranges skipped by the preprocessor and expose them with libclang.

Patch by Erik Verbruggen!