Gives an opportunity to execute the code on bit level, assigning
symbolic values to the variables which don't have initial values.
Supports only CRC specific operations.

Example:

uint8_t crc;
uint8_t pol = 1;
crc = crc ^ pol;

during symbolic execution crc's value will be:
crc(8), crc(7), ... crc(1), crc(0) ^ 1

gcc/
	* Makefile.in (OBJS): Add sym-exec/sym-exec-expression.o,
	sym-exec/sym-exec-state.o, sym-exec/sym-exec-condition.o.
	* configure (sym-exec): New subdir.
	* sym-exec/sym-exec-condition.cc: New file.
	* sym-exec/sym-exec-condition.h: New file.
	* sym-exec/sym-exec-expr-is-a-helper.h: New file.
	* sym-exec/sym-exec-expression.cc: New file.
	* sym-exec/sym-exec-expression.h: New file.
	* sym-exec/sym-exec-state.cc: New file.
	* sym-exec/sym-exec-state.h: New file.

Co-authored-by: Mariam Arutunian <mariamarutunian@gmail.com>