Use float version of sqrt from newlib

The previous version was using doubles, and assuming they were 64 bits. Although
AVR only has 32 bit doubles. Use floats instead.

	* src/newlib-sqrt/Makefile.am: Rename e_sqrt to ef_sqrt
	* src/newlib-sqrt/Makefile.in: Regenerate
	* src/newlib-sqrt/e_sqrt.c: Delete
	* src/newlib-sqrt/ef_sqrt.c: Import ef_sqrt from newlib
Add exp from newlib.

	* Makefile.am: Add src/newlib-exp to SUBDIRS
	* Makefile.in: Regenerate
	* analysis/simulator.in: Add newlib-exp benchmark
	* configure: Regenerate
	* configure.ac: Add src/newlib-exp/Makefile to AC_CONFIG_FILES
	* src/newlib-exp/Makefile.am: Create Makefile.am from template
	* src/newlib-exp/Makefile.in: Regenerate
	* src/newlib-exp/ef_exp.c: Import ef_exp from newlib