Gwenhywfar

OS: Allow GWEN_Process_RunCommandWaitAndGather() to also read stderr.

This is currently only implemented on non-win32 systems.
For win32 we will have to implement GWEN_Process_WaitAndRead() which
needs non-blocking access to pipes created by CreatePipe()....

gwenbuild: More work, implemented some more XML elements from build files.

OS/POSIX: GWEN_Process_Start() now uses GWEN_StringList_fromString2().

Also untangled spaghetti code.

OS: Added function GWEN_Process_RunCommandWaitAndGather().

This function runs a command and reads its output to a buffer.

BASE: Added function GWEN_StringList_fromString2().

This function internally uses the powerfull function
GWEN_Text_GetWordToBuffer().

gwenbuild: Preset "prefix".

gwenbuild: Target now parses <sources> and <headers>.

gwenbuild: Add functions to get and set install path. Defined flags.

gwenbuild: Added missing copy code for currentRelativeDir.

gwenbuild: Created a framework to read a build tree.

Only a few entries are currently picked up but that will be improved upon
int following commits.

XML: Added function GWEN_XMLNode_ExpandProperties().

gwenbuild: Write project info into db of current context.

- these vars will be inherited by each child-context.

gwenbuild: Started working on main object.

- copy some important environment variables to DB of the main context
- expand variables from current context on GWB_Parser_ReadXmlDataIntoStringList()

gwenbuild: More work on parser.

- added function GWB_Parser_ReadBuildTree()
- added context as an argument to GWB_Project_new()

gwenbuild: Started working on build file parser.

gwbuild: More work.

Merge branch 'master' into mp-202102-gwenbuild

test: Added a test for setting big binary data to GWEN_DB.

XML: Fixed indentation.

BUFFER: Added GWEN_Buffer_KeepTextBetweenStrings and tests for it.

OS: More work on threads.

Added functions to set flags. Those are used when creating a thread.
The only flag currently available allows for creating undetached threads
(currently only on POSIX systems, on Windows the resources must always be
released with CloseHandle())....

Build: Add warning option to compiler flags.

OS: Added argument to GWEN_Semaphore_new().

Updated gource script.

OS: Export semaphore symbols.