Improve relative>absolute filename option handling

Relative -> absolute filename handling now occurs for the following flags:
 -I
 -F
 -iquote
 -include

Rather than just -I.

Backslashes are now no longer erroneously removed, and can be used as an
escape character on posix systems.

Relative->absolute filename handling should be more robust in general.
fixed bash path in Makefile

Signed-off-by: Oliver Pinter <oliver.pntr@gmail.com>
Make all include path absolute, so that it is no longer needed to change the working directory
Add global functions for GotoDeclaration().
Add GotoDeclaration functions to documentation.
Merge pull request #402 from kevincox/master

Made GotoDeclaration functions public.
Merge pull request #390 from Andrew-Dunn/better_absolute_paths

Improve relative>absolute filename option handling
Merge pull request #400 from opntr/master

fixed bash path in Makefile
Merge pull request #403 from Arnaud-de-Grandmaison/issue372

Make all include path absolute, so that it is no longer needed to change...
Makefile fix: SHELL should be set to /usr/bin/env bash not $(/usr/bin/env bash)
Merge pull request #404 from crucerucalin/master

Makefile fix: SHELL should be set to /usr/bin/env bash not $(/usr/bin/en...