GT 0063 Emulation Enhancements

1. EPOCROOT check in E32env.PM

Changed from static data to an active BEGIN{} section which tests the EPOCROOT
environment variable and constructs the rest of the E32env::Data hash accordingly.

EPOCROOT checking is:

 - environment variable must exist
 - EPOCROOT must begin with \
 - EPOCROOT must specify an existing directory

Most clients are expected to use $E32Env::Data{EPOCPath} as the raw "epoc32" directory.


2. Path_MakeEAbs in PATHUTL.PM

Variant of Path_MakeAbs.
Path_MakeEAbs takes (EPOCPath, BasePath, ...) and makes the list of directories into 
absolute paths relative to BasePath. The extra functionality is that paths beginning

	+\...

are treated as paths relative to EPOCPath rather than BasePath. 

As a regression change, this change also extends to paths which begin \epoc32\, which 
copes with the large number of existing absolute \epoc32 paths (e.g. SYSTEMINCLUDE 
statements in MMP files). 

Path_MakeEAbs is used in MMP.PM to handle SYSTEMINCLUDE, DEFFILE and USERINCLUDE
statements, and in BLDMAKE.PL to handle PRJ_EXPORTS and PRJ_TESTEXPORTS.
