Improved strong/emph parsers to avoid exponential blowup.

Closes #18.
Require only one character for setext header lines.

This is explicit in Gruber's syntax description.
Closes #17.
Removed unused parser.
Bumped version to 0.4.13.
Fixed Endline to allow 1 and 2-character setext header lines.
Rewrote Emph/Strong parsers to avoid exponential blowup.

Closes #19.
Removed unused disjunct in SourceContents.
Bump version to 0.4.14.
Efficiency improvement (!Whitespace instead of &Nonspacechar).
Upgrade from peg 0.1.4 to peg 0.1.9
Merge pull request #20 from rekado/upgrade-peg

Upgrade from peg 0.1.4 to peg 0.1.9
Removed unneeded peg-memory-fix.patch.
Fix makefile to build peg, remove peg-exe-ext.patch
Refactoring to build on windows

all .c files now build as separate files.
code has been refactored to not depend on inclusion of .c files
functions in utility_functions.c are now extern
removed strdup and strcasecmp prototypes, now use .h files
fixed inconsistent linkages in markdown_output.c
Fixed distclean so it doesn't wipe out peg directory.
Removed optimization flag that requires newer GCC.
Only obfuscate ascii characters.

See fletcher/peg-multimarkdown/issues/139 for background.
Treat <head> as block-level HTML tag.

Closes #21.