Backport various improvements from Tcl 8.5
merge-mark
Add some extra paths on Windows for fincing tclConfig.sh, for mSys and Cygwin shell.
Improve some comments and quoting, no change in functionality
Improve some comments and quoting, no change in functionality. 
Only check for refCount == 0x61616161 for TCL_MEM_DEBUG build.
Suggested fix for bug 3604576: msgcat -1.5.0.tm error on windows XP, inclusive bump to version 1.5.1.
Changelog entry still missing.
Finer granulated catch
[Bug 3604576]: msgcat-1.5.0.tm error on windows XP
[Bug 3604576]: msgcat-1.5.0.tm error on windows XP
ChangeLog corrected: msgcat issue must not be XP specific
ChangeLog corrected: msgcat issue must not be XP specific
merge-mark
Eliminate last use of Tcl_SetResult (except the use in the Test suite)
Fix depreciation message in tcl.h
merge trunk: