fast c-string transformations

Hello!

I don't use this library anymore and try to avoid C programming if possible. That said, I'm very happy to accept pull-requests and collaborators.

• You'll need to install autoconf, automake and libtool
• run ./bootstrap.sh
• run ./configure
• run make && make check

• modp_base64_decode expects aligned strings as input. For Intel, is doesn't matter. But for ARM chips it can segfault.
• modp_numtoa.c functions may produce different rounding than whatever printf is on your system.
• On mingw (windows) compiling with -D__USE_MINGW_ANSI_STDIO gives the standard prinf behavior.

• As mentioned, the tests for modp_numtoa.c may fail due to a different rounding algorithm.
• https://wiki.alpinelinux.org/wiki/How_to_get_regular_stuff_working
• apk add gcc bash autoconf automake libtools util-linux pciutils usbutils coreutils binutils findutils grep