Refactor docs files for bcmath library

ext/bcmath/libbcmath/README.md

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+# The bcmath library
+
+This is a fork of the bcmath library initially created by Phil Nelson in May
+2010.
+
+Bcmath is a library of arbitrary precision math routines. These routines, in a
+different form, are the routines that to the arbitrary precision calculations
+for GNU bc and GNU dc.
+
+This library is provided to make these routines useful in a larger context with
+less restrictions on the use of them.
+
+These routines do not duplicate functionality of the GNU gmp library. The gmp
+library is similar, but the actual computation is different.
+
+Initial library (version 0.1) has been created in 2000-05-21 and then forked and
+bundled into PHP with version 0.2 released in 2000-06-07.
+
+## FAQ
+
+* Why BCMATH?
+
+  The math routines of GNU bc become more generally useful in a library form. By
+  separating the BCMATH library from GNU bc, GNU bc can be under the GPL and
+  BCMATH can be under the LGPL.
+
+* Why BCMATH when GMP exists?
+
+  GMP has "integers" (no digits after a decimal), "rational numbers" (stored as
+  2 integers) and "floats". None of these will correctly represent a POSIX BC
+  number. Floats are the closest, but will not behave correctly for many
+  computations. For example, BC numbers have a "scale" that represent the number
+  of digits to represent after the decimal point. The multiplying two of these
+  numbers requires one to calculate an exact number of digits after the decimal
+  point regardless of the number of digits in the integer part. GMP floats have
+  a "fixed, but arbitrary" mantissa and so multiplying two floats will end up
+  dropping digits BC must calculate.
+
+## Credits
+
+Phil Nelson (philnelson@acm.org) wrote bcmath library.
+
+## License
+
+The bcmath library is released under the GNU Lesser General Public License v2.1.