* src/mcs51/rtrack.h,

* src/mcs51/rtrack.h,
* src/mcs51/rtrack.c: added register tracking for the mcs51 port, by checking the strings passed by emitcode() to the assembler.
Feel free to change. This in part addresses RFE #482179.
Set environment variable SDCC_RTRACK to enable.
* src/mcs51/gen.c: inserted hooks
* src/mcs51/ralloc.h: added two members to struct regs
* support/regression/tests/regtrack.c: added

git-svn-id: https://sdcc.svn.sourceforge.net/svnroot/sdcc/trunk/sdcc@4634 4a8a32a2-be11-0410-ad9d-d568d2c75423