create "tool frontend" library

From [email protected] on February 14, 2013 23:41:35

DR-based tool frontends will typically share a lot beyond just drinjectlib and drconfiglib.

Right now we're considering sharing utf8 support from DrMem's frontend.c with DR's drdeploy.c (xref issue i43).

Plus the strace tool's frontend ends up wanting a pretty exact copy of a subset of DrMem's frontend, leading to:

/* XXX: share as much of this code as possible with drmem's frontend.c.

Currently this is all a copy based on frontend.c. *
Perhaps we should build a library with a common set of front-end
options and features: utf8, path search and absolute conversion
and canonicalization, DR location, client lib location, DR and client
lib debug vs release, DR and client options, etc. */

/* FIXME: have an optionsx.h or what? Shared frontend lib could help
- solve that by providing usage and options parsing for its provided
- options. */