Changes from Version 1.0 to Version 1.1.

V1.0 read the Makefile line by line into buffer, merging continuation
lines with no overflow checking. V1.1 reads the entire Makefile into memory
and does continuation merging in place.

V1.0 only deferenced variables in the script which were known to have been
defined or referenced in the Makefile.  V1.1 dereferences all variables in
the script; if a variable wasn't given a value in the Makefile, it's assumed
to have an empty value.

V1.0 allowed no way to define alternate reference indicators in the template.
V1.1 allows that using +R/-R.  This allows better disambiguation of variable
references in shell scripts.

V1.11 Added support for -e and variable=value options on the command line.