calc 2.14.1.5 release

The following are the changes in this release:

Fixed version numbers in two cases in CHANGES that referred
to the 2.14.2.x instead of 2.14.1.x.

Rename MINGW Makefile variable (a holdover from MINGW32_NT-5.0)
to OSNAME.

Fixed FUNCPTR typedef in hist.c to fix deprecated compiler warnings.

Fixed when USE_READLINE, READLINE_LIB, READLINE_EXTRAS, and
READLINE_INCLUDE are set to empty (disable use of the GNU-readline
facility).

Fix cases of spaces before tabs in Makefile and Makefile.simple.