Add support for path prefix replacement

[Farigh]

Sometimes the backtrace could contain paths that are not relevant in the report (too long or environment dependent path for example).

The idea would be to allow users to define prefixes, optionally with a possible replacement.

For example, the following report:

==1== Conditional jump or move depends on uninitialised value(s)
==1==    at 0x10101042: myFunc() (/a/directory/path/on/my/machine/myotherprojectsrc/mylibs/lib1/MyClass.cpp:14)
==1==    by 0x10101042: main (/a/directory/path/on/my/machine/myprojectsrc/main.cpp:34)
==1==  Uninitialised value was created by a stack allocation
==1==    at 0x10101042: myFunc() (/a/directory/path/on/my/machine/myotherprojectsrc/mylibs/lib1/MyClass.cpp:5)

Could be tweeked in the config file:

memcheck_report_path_prefix_replacement["/a/directory/path/on/my/machine/myotherprojectsrc"]="<my lib project src>"
memcheck_report_path_prefix_replacement["/a/directory/path/on/my/machine/myprojectsrc"]="<my bin project src>"

And the generation would look like this:

==1== Conditional jump or move depends on uninitialised value(s)
==1==    at 0x10101042: myFunc() (<my lib project src>/mylibs/lib1/MyClass.cpp:14)
==1==    by 0x10101042: main (<my bin project src>/main.cpp:34)
==1==  Uninitialised value was created by a stack allocation
==1==    at 0x10101042: myFunc() (<my lib project src>/mylibs/lib1/MyClass.cpp:5)